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DCs are a complex cell population in the skin consisting of epidermal LCs and dermal DCs, which differ in their anatomic location, antigen recognition, processing machinery, and migratory capacity. Cutaneous DCs (LCs as well as dermal DCs) function as sentinels that survey invading agents and transmit the information into immune responses by taking up exogenous antigens, migrating to draining LNs, and presenting the processed antigens to T cells resulting in T-cell differentiation and activation. Indeed, further studies are needed to clarify the specific contribution of each cutaneous DC subpopulation to antigen presentation and induction of cutaneous immune responses. Recent results suggested to revisit the "paradigm" that exclusively immigrant LCs present skin-acquired antigens to T cells upon reaching the draining LNs, because viral antigens, for instance, are presented by a DC subpopulation other than LCs after infection of mouse epidermis with herpes simplex virus [153]. Additionally, different DC subpopulations may sequentially present skin-acquired antigens, possibly serving as a regulatory mechanism of cell-mediated immunity and adding further complexity to established concepts. Nevertheless, cutaneous DCs are involved in several pathologies (including infections, inflammatory disorders, or skin cancers) and play a pivotal role in regulating the balance between immunity and peripheral tolerance. However, it is widely accepted that (cutaneous) DC in an immature state may have tolerogenic properties resulting in the induction or expansion of Tregs. CD4+CD25+ Tregs are essential for the control of immune responses in inflammatory, autoimmune, or cancer diseases, and it is well established that in particular the lineage-specific transcription factor Foxp3, as well as cytokines (including IL-2, IL-10, and TGF-beta), characteristic surface markers such as CTLA-4, and members of the TNF superfamily (e.g., RANKL) are critically involved in the thymic development, peripheral maintenance, and suppressive activity of CD4+CD25+ Tregs. Recently, new methods for generating and expanding Tregs in vitro have emerged and supported the use of CD4+CD25+ T cells as a novel strategy for the treatment of patients suffering from autoimmune diseases. In the future, a better understanding of Treg function in vivo and the interactions of Tregs and pathogenic effector T cells in autoimmune disorders may help to improve the design of Treg-based therapies.

Regulatory CD4(+)CD25(+) T cells are important in suppressing immune responses. The requirements for the maintenance of peripheral CD4(+)CD25(+) T cells remain incompletely understood. Receptor activator of NF-kappaB (RANK) and its ligand (RANKL; also known as CD254, OPGL and TRANCE) are key regulators of bone remodeling, mammary gland formation, lymph node development and T-cell/dendritic cell communication. Here we report that RANKL is expressed in keratinocytes of the inflamed skin. RANKL overexpression in keratinocytes resulted in functional alterations of epidermal dendritic cells and systemic increases of regulatory CD4(+)CD25(+) T cells. Thus, epidermal RANKL expression can change dendritic cell functions to maintain the number of peripheral CD4(+)CD25(+) regulatory T cells. Epidermal RANKL mediated ultraviolet-induced immunosuppression and overexpression of epidermal RANKL suppressed allergic contact hypersensitivity responses and the development of systemic autoimmunity. Therefore, environmental stimuli at the skin can rewire the local and systemic immune system by means of RANKL.

The adaptive immune response is initiated when naive T cells interact with dendritic cells (DC). However, the physicodynamics as well as the molecules that constitute the contact plane (immunological synapse) between DC and T cells are not well understood. We show here that for the formation of stable conjugates, T cells need to be preactivated by DC in a CD80/86- and antigen dose-dependent manner. When activated, T cells induce cytoskeletal reorganization within DC via CD40-CD40L signaling. Polarization of the actin and fascin cytoskeleton in DC is associated with sustained DC-T cell contacts, strong T cell proliferation and a Th1 response. Organized contact planes with clearly separated patches containing TCR or CD11a are also formed. Thus, DC-T cell interactions take place in a sequential, interdependent fashion: first, DC "license" naive T cells to engage DC in an antigen dose- and CD80/86-dependent fashion. Then, these preactivated T cells induce cytoskeletal reorientation in DC, resulting in sustained DC-T cell contacts and subsequent T cell activation. These results demonstrate that T cells control the mode of interaction based on information gathered from DC.

Objective: To investigate the safety and efficacy of oral methylprednisolone combined with azathioprine sodium or mycophenolate mofetil for the treatment of pemphigus., Design: A prospective, multicenter, randomized, nonblinded clinical trial to compare 2 parallel groups of patients with pemphigus (pemphigus vulgaris and pemphigus foliaceus) treated with oral methylprednisolone plus azathioprine or oral methylprednisolone plus mycophenolate mofetil. Settings Thirteen departments of dermatology in Germany. Patients We included patients with pemphigus vulgaris (n = 33) or pemphigus foliaceus (n = 7) evidenced by clinical lesions suggestive of pemphigus, intraepidermal blistering on histological analysis of skin biopsy specimens, intercellular deposition of IgG within the epidermis, and immunoblot analysis findings for antidesmoglein 3 and/or antidesmoglein 1 autoantibodies., Main Outcome Measures: The cumulative total methylprednisolone doses and rate of remission. Secondary outcome measures were safety profiles and duration of remission., Results: In 13 (72%) of 18 patients with pemphigus receiving oral methylprednisolone and azathioprine, complete remission was achieved after a mean +/- SD of 74 +/- 127 days compared with 20 (95%) of 21 patients receiving oral methylprednisolone and mycophenolate mofetil in whom complete remission occurred after a mean +/- SD of 91 +/- 113 days. The total median cumulative methylprednisolone dose used was 8916 mg (SD, +/-29 844 mg) in the azathioprine group compared with 9334 mg (SD, +/-13 280 mg) in the mycophenolate group. In 6 (33%) of 18 patients treated with azathioprine, grade 3 or 4 adverse effects were documented in contrast to 4 (19%) of 21 patients who received mycophenolate mofetil. Conclusion Mycophenolate mofetil and azathioprine demonstrate similar efficacy, corticosteroid-sparing effects, and safety profiles as adjuvants during treatment of pemphigus vulgaris and pemphigus foliaceus.

Our views of the skin immunity theatre are undergoing constant change. These not only reflect paradigm shifts in general immunology and skin biology, but also have profound clinical implications, which call for strategic changes in dermatological therapy. Nowhere can this be witnessed at a greater level of instructiveness and fascination than when addressing the question posed by this new Controversies feature. Thus, after a very long period of dominance by T cells and Langerhans cells as 'lead actors' on the skin immunity stage, the lowly keratinocyte has recently made an astounding theatrical appearance as a key protagonist of the innate skin immunity system, which may control even acquired skin immune responses. Further enhancing dramatic complexity and tension, the mast cell has entered as an additional actor claiming centre stage, and the epidermal Langerhans cell has slipped in a surprise appearance as the chief agent of immunotolerance. May you, esteemed reader, enjoy the spectacle offered here by selected immunodermatology authorities who double as 'stage managers' pushing their respective favourite actors into the limelight. You get everything you may expect from a good performance - complete with the impresario's overture that lures you into the theatre and sets the stage, competing divas, recently discovered new talents and even the critic's digest while the performance is still ongoing. By the time the curtain drops, you will have reached your own, independent conclusions on how to answer the title question of this play - at least for the time being...

Immature dendritic cells (DC) reside in tissues where they initiate immune responses by taking up foreign antigens. Since DC have a limited tissue half-life, the DC pool in tissues has to be replenished constantly. This implies that precursor/immature DC must be able to cross non-activated endothelium using as yet unknown mechanisms. Here we show that immature, but not mature bone marrow-derived murine DC migrate across resting endothelial monolayers in vitro. We find that endothelial intercellular adhesion molecule-2 (ICAM-2) is a major player in transendothelial migration (TEM) of immature DC, accounting for at least 41% of TEM. Surprisingly, the ICAM-2-mediated TEM was independent of beta2-integrins, the known ICAM-2 ligands, since neither blocking of beta2-integrins with antibodies nor the use of CD18-deficient DC affected the ICAM-2-specific TEM. In humans, the C-type lectin DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN) was shown to interact with ICAM-2, suggesting a similar role in mice. However, we find that none of the murine DC-SIGN homologues mDC-SIGN, murine DC-SIGN-related molecule-1 (mSIGN-R1) and mSIGN-R3 is expressed on the surface of bone marrow-derived mouse DC. Taken together, this study shows that ICAM-2 strongly supports transmigration of immature DC across resting endothelium by interacting with ligands that are distinct from beta2-integrins and DC-SIGN homologues.

In systemic sclerosis (SSc; scleroderma) fibrosis of the skin can lead to considerable morbidity. No significant improvement has been reported from studies investigating antifibrotic therapies so far. In dermatology, phototherapy with ultraviolet (UV) irradiation is successfully used for treatment of several diseases because of its anti-inflammatory as well as immunosuppressive mechanisms, and its low-risk profile. In addition, the UVA spectrum in particular exerts antifibrotic effects as it leads to reduction of procollagen synthesis and expression of collagenase-1 in vitro. Accordingly, treatment with long-wavelength UVA-1 irradiation or photochemotherapy with UVA plus the photosensitizer psoralen (PUVA) have been successfully used to reduce skin fibrosis in localized scleroderma (morphea). There are only in particular few reports on treatment of skin sclerosis in SSc, but the results are in concordance with the good experience that have been observed at our and other dermatological centres. Phototherapy is able to stop or inhibit the fibrotic processes and to induce softening of sclerotic skin, especially in limited SSc. Phototherapy thus represents a therapeutic alternative for antifibrotic treatment with a low rate of adverse effects, which should be applied before the sclerotic process has proceeded too far.

Cutaneous autoimmunity is characterized by the presence of autoantibodies and/or autoreactive T cells. Several mechanisms have been developed to avoid loss of immunotolerance to self such as activation-induced cell death, deletion, ignorance and active suppression of autoreactivity. Regulatory ('suppressor') T cells play a pivotal role in inhibiting the activation and function of effector T cells. CD4(+)CD25(+) T cells constitute a subset of regulatory T cells, which have been shown to suppress the development of organ-specific autoimmunity in mice. Recent understanding in the generation and function of human regulatory T cells indicates that these cells are involved in the appearance of inflammatory as well as bullous autoimmune dermatosis. These findings suggest that modulation of regulatory T cell numbers or function might be a promising therapeutic alternative for the treatment of such disorders. In the following, recent strategies aimed at inducing antigen-specific or non-specific regulatory T cells for the immunotherapy of ongoing cutaneous autoimmunity are presented and discussed. Hopefully, pursuing these strategies in the future will result in the initiation of randomized clinical studies analysing the usefulness of regulatory T cells for human skin diseases in great detail.

Foxp3 functions as a lineage specification factor for the development of naturally occurring thymus-derived CD4+CD25+ regulatory T (Treg) cells. Recent evidence suggests that naive Foxp3-CD4+CD25- T cells can be converted in the periphery into Foxp3+ Treg cells. In this study, we have identified the G protein-coupled receptor (GPR)83 to be selectively up-regulated by CD4+CD25+ Treg cells of both murine and human origin in contrast to naive CD4+CD25- or recently activated T cells. Furthermore, GPR83 was induced upon overexpression of Foxp3 in naive CD4+CD25- T cells. Transduction of naive CD4+CD25- T cells with GPR83-encoding retroviruses did not confer in vitro suppressive activity. Nevertheless, GPR83-transduced T cells were able to inhibit the effector phase of a severe contact hypersensitivity reaction of the skin, indicating that GPR83 itself or GPR83-mediated signals conferred suppressive activity to conventional CD4+ T cells in vivo. Most strikingly, this in vivo acquisition of suppressive activity was associated with the induction of Foxp3 expression in GPR83-transduced CD4+ T cells under inflammatory conditions. Our results suggest that GPR83 might be critically involved in the peripheral generation of Foxp3+ Treg cells in vivo.

Autoimmunity results from loss of mechanisms controlling self-reactivity. Autoimmune disorders play an increasingly important role and CD40-CD40 ligand (CD40L) interaction on immunocompentent cells is able to break established immunotolerance. To study the effects of the calcineurin-inhibitor FK506 on CD40L-induced systemic autoimmunity, CD40L transgenic (tg) mice, which spontaneously develop a mixed connective tissue-like disease, were treated with FK506 after onset of overt autoimmunity. Interestingly, FK506-treated CD40L tg mice showed significantly reduced autoimmune dermatitis scores and markedly decreased numbers of lesional infiltrating leukocytes. This finding was associated with diminished lymphadenopathy induced by FK506 treatment. Furthermore, FK506 suppressed the development of cytotoxic/autoreactive CD8(+) T cells as evidenced by the reduced expression of T cell activation markers in treated CD40L tg mice. Importantly, FK506 induced a significant reduction in autoantibody titers in the serum of CD40L tg animals. As CD40L tg mice develop nephritis leading to loss of renal function proteinuria was determined after FK506 injections. Notably, FK506 treatment re-established renal function as indicated by significantly reduced uric protein concentrations of treated CD40L tg mice. Together, these findings show the beneficial therapeutic effects of FK506 for the treatment of CD40L-induced autoimmunity. Additionally, these results demonstrate that FK506 is able to suppress ongoing severe autoimmune responses.

UV-induced DNA damage is the basis for the development of UV-mediated skin cancer because reduction of DNA damage lowers the risk for photocarcinogenesis. The cytokine interleukin (IL)-12 was shown to exhibit the capacity to reduce UV-induced DNA damage presumably via induction of nucleotide excision repair. Because IL-12 is also produced in the skin, we wondered whether endogenous IL-12 protects from photocarcinogenesis. Therefore, we used knockout mice that lack the IL-12p40 chain and thus do not secrete biologically active IL-12. IL-12p40 knockout (IL-12p40-/-) and wild-type (wt) mice were exposed thrice weekly to UV. Skin biopsies obtained after 6 weeks revealed significantly increased numbers of sunburn cells in IL-12p40-/- mice. Additionally, a higher load of UV-induced pyrimidine dimers could be detected in the skin of UV-exposed IL-12p40-/- mice. Staining of epidermal sheets with an antibody against the tumor suppressor gene p53 revealed a higher number of p53 patches in the skin of IL-12p40-/- mice. After approximately 200 days, first skin tumors developed. Kaplan-Meier analysis indicated a significantly increased probability of tumor development in the IL-12p40-/- mice. In addition, the number of tumors developing in the individual mice was significantly higher in IL-12p40-/- mice than in wt mice. Tumors obtained in IL-12p40-/- mice grew faster than those obtained from wt mice on inoculation into nu/nu mice. This was confirmed in an electrophysiologic assay evaluating the intrinsic invasive potency of tumor cells. Together, these data indicate that IL-12 deficiency is associated with an increased risk to develop UV-induced skin cancer, implying that endogenous IL-12 may protect from photocarcinogenesis.

Pemphigus vulgaris (PV) is a severe autoimmune bullous skin disorder and is associated with autoantibodies against desmoglein (Dsg)3 that are regulated by Th2 cells. Recently, Dsg3-specific type 1 regulatory T cells (Tr1) were identified that are presumably critical for the maintenance of tolerance against Dsg3 because there is a much lower Dsg3-specific Tr1:Th2 ratio in the PV patients than in healthy individuals. The aim of this study was to down-regulate the transcription factor Foxp3 in Dsg3-specific Tr1 using antisense oligonucleotides because Foxp3 is constitutively expressed by the Dsg3-specific Tr1. Antisense-treated Dsg3-specific Tr1 clones lost expression of Foxp3, glucocorticoid-induced TNFR family-related receptor, and CTLA-4, and started to secrete IL-2, whereas the secretion of IL-5, TGF-beta, and IL-10 remained unchanged. Moreover, antisense treatment induced a proliferative response to Dsg3 of the formerly anergic Tr1 and abrogated their suppressor activity on Dsg3-specific Th2 cell clones. Thus, inhibition of Foxp3 mRNA expression in the Tr1 induced a Th2-like phenotype. In conclusion, Foxp3 expression is inherent to Tr1 function, and modulation of Foxp3 expression in autoaggressive Th2 cells may provide a novel therapeutic approach aimed at restoring tolerance against Dsg3 in PV.

The skin is a frequent site of pathological immune responses that can take place in the dermal and/or the epidermal compartments.These immunopathological reactions often occur towards innocuous antigens and may be the result of T cell-dependent and/or autoantibody dependent mechanisms. Defective immune regulation is increasingly recognized as very relevant in many skin and systemic immune-mediated disorders. In some instances (e.g., psoriasis and atopic dermatitis) genetic predisposition can affect also the capacity of keratinocytes to initiate or perpetuate inflammatory responses. A more precise understanding of the molecular and cellular mechanisms underlying each disorder may allow the identification of novel targets for more effective therapeutic strategies.

Immunologic self-tolerance is critically dependent on the induction but also on the downregulation of immune responses. Though ignored and neglected for many years, suppressor T cells, now renamed regulatory T cells (Tregs), play an important role in the negative regulation of immune responses. Several subsets of Tregs have been described. Naturally occurring CD4(+)CD25(+) Tregs are important in the prevention of autoimmune diseases. Type 1 Tregs, another subtype of Treg that is inducible, exert their suppressive activity primarily via the release of IL-10. Detailed knowledge about the phenotype and mode of action of these cells will significantly increase our understanding of the pathogenesis of autoimmune diseases and will also help to identify new therapeutic strategies.

Lupus erythematosus (LE) is an autoimmune disease which can be triggered by environmental factors such as solar irradiation. It has long been observed that especially ultraviolet (UV) exposure can induce and exacerbate skin lesions in patients with this disease. However, despite the frequency of photosensitivity in LE, the mechanisms by which UV irradiation activates autoimmune responses is only now becoming increasingly unfolded by advanced molecular and cellular biological investigations. Phototesting, according to a standardized protocol with UVA and UVB irradiation has proven to be a valid model to study photosensitivity in various subtypes of LE and to evaluate the underlying pathomechanisms of this disease. Detailed analysis of the molecular events that govern lesion formation in experimentally photoprovoced LE showed increased accumulation of apoptotic keratinocytes and impaired expression of the inducible nitric oxide synthase (iNOS). In the near future, gene expression profiling and proteomics will further increase our knowledge on the complexity of the "UV response" in LE. This review summarizes the current understanding of the clinical and molecular mechanisms that initiate photosensitivity in this disease.

Epicutaneous application of dinitrothiocyanobenzene (DNTB) induces tolerance against its related compound dinitrofluorobenzene (DNFB), because DNTB-pretreated mice cannot be sensitized against the potent hapten DNFB. This tolerance is hapten-specific and transferable. In this study, we demonstrate that IL-12 can break DNTB-mediated tolerance. Furthermore, naive mice treated with IL-12 before DNTB application responded to DNFB challenge with a pronounced ear swelling response without previous sensitization to DNFB, showing that IL-12 can convert the tolerogen DNTB into an immunogen. No differences in numbers or regulatory activity were observed between CD4+CD25+ regulatory T cells isolated from mice treated with DNFB, DNTB, or IL-12 followed by DNTB. However, the number of CD207+ Langerhans cells in regional lymph nodes of DNTB-treated mice was significantly lower than in animals treated with DNFB or IL-12 plus DNTB. Additionally, CD11c+ dendritic cells (DC) isolated from regional lymph nodes of DNTB-treated mice had a significantly lower ability to stimulate T cell proliferation and produced reduced amounts of inflammatory cytokines. Application of both DNFB and DNTB induced apoptotic cell death of DC in the epidermis and the regional lymph nodes. However, the number of apoptotic DC in regional lymph nodes was significantly higher in DNTB-treated animals compared with mice treated with DNFB or IL-12 plus DNTB. Therefore, we conclude that DNTB-mediated tolerance is secondary to inefficient Ag presentation as a result of apoptotic cell death of DC and that IL-12 converts the tolerogen DNTB into an immunogen by preventing DNTB-induced apoptosis of DC.

Protection against ultraviolet (UV) irradiation prevents from the development of acute skin damage such as erythema formation and chronic skin changes such as premature skin ageing. Especially those sunscreens with higher sun protection factors do not only protect against solar dermatitis but also inhibit UV-induced immunosuppression by blocking the release of immunosuppressive mediators from UV-exposed epidermis. In particular, the protection against UV-induced immunosuppression by sunscreens is supposed to reduce the development of UV-induced skin cancer. Besides immunosuppression UV-irradiation is also able to induce "UV signature" mutations within UV-exposed DNA. Topical application of DNA repair enzymes induces nucleotide excision repair and corrections of DNA damages. Thereby, the risk to develop UV-induced skin malignancies is markedly reduced. Accordingly, future perspectives in the development of sunscreens include DNA repair enzymes or factors, which can induce the endogenous cellular DNA repair system. Until these developments come to practice reasonable sun protection according to the skin complexion is of primary importance.

Regulatory T cells are promising candidates for the modulation of inflammation and autoimmunity. To generate regulatory T cells in vitro, we have infected naïve CD4+CD25- T cells with a retrovirus encoding the transcription factor Foxp3. Foxp3-infected T cells are similar to naturally occurring regulatory T cells as evidenced by surface marker expression and function. To investigate the effects of Foxp3-infected T cells on contact hypersensitivity (CHS) responses, sensitized mice were injected with Foxp3- or control virus-infected T cells. Only injection of Foxp3-infected T cells into sensitized mice significantly inhibited CHS compared to controls, indicating that Foxp3-infected T cells are suppressive in vivo. These findings prompted treatment of autoimmune-prone CD40L transgenic (tg) mice, which develop a severe systemic autoimmune disease including autoreactive T cells and autoantibodies, with Foxp3-infected T cells. Interestingly, injections of Foxp3-infected T cells into CD40L tg mice inhibited the ongoing development of autoimmune dermatitis and activation of cytotoxic CD8+ T cells. Strikingly, treatment with Foxp3-infected T cells reduced serum concentrations of antinuclear antibodies in CD40L tg mice, which was paralleled with reduced renal immunoglobulin depositions and increased kidney function. Together, these findings indicate that newly in vitro-generated regulatory T cells can be successfully used to treat inflammatory and ongoing autoimmune disorders.

Although previous studies have shown that altered B7 costimulation plays a critical role in UV irradiation-induced regulation of immunity, the individual roles of the B7 receptors (CD28 and CTLA-4) or the B7 family members (CD80 and CD86) have not been explored. Thus, we investigated CTLA-4 signaling during photocarcinogenesis of chronically UV-B-exposed mice using an antagonistic anti-CTLA-4 Ab. Anti-CTLA-4-treated mice developed significantly fewer UV-induced tumors. Moreover, anti-CTLA-4 treatment induced long-lasting protective immunity because progressively growing UV tumors inoculated into anti-CTLA-4- and UV-treated mice that had not developed tumors were rejected. Next, we used mice deficient for CD80, CD86, or both in photocarcinogenesis studies to assess the relative contributions of these CTLA-4 ligands. Double-deficient mice showed significantly reduced UV-induced skin tumor development, whereas CD86(-/-) mice produced skin cancer earlier compared with CD80(-/-) and control mice. The growth of UV-induced tumors appears to be controlled by UV-induced suppressor T cells, because CD80(-/-)/CD86(-/-) mice had strongly reduced numbers of UV-induced CD4(+)CD25(+) suppressor T cells. In vitro, CTLA-4 blockade inhibited the suppressor activity of UV-induced CD4(+)CD25(+) T cells, suggesting that reduced photocarcinogenesis might be due to decreased numbers or function of suppressor T cells. Together, these data indicate that blocking CD80/86-CTLA-4 signaling induced immune protection against the development of UV-induced skin tumors. Furthermore, CD86-mediated costimulation appears to play a more critical role in the protection against photocarcinogenesis than CD80.

The immunostimulatory cytokine IL-12 is able to antagonize immunosuppression induced by solar/ultraviolet (UV) radiation via yet unknown mechanisms. IL-12 was recently found to induce deoxyribonucleic acid (DNA) repair. UV-induced DNA damage is an important molecular trigger for UV-mediated immunosuppression. Thus, we initiated studies into immune restoration by IL-12 to discern whether its effects are linked to DNA repair. IL-12 prevented both UV-induced suppression of the induction of contact hypersensitivity and the depletion of Langerhans cells, the primary APC of the skin, in wild-type but not in DNA repair-deficient mice. IL-12 did not prevent the development of UV-induced regulatory T cells in DNA repair-deficient mice. In contrast, IL-12 was able to break established UV-induced tolerance and inhibited the activity of regulatory T cells independent of DNA repair. These data identify a new mechanism by which IL-12 can restore immune responses and also demonstrate a link between DNA repair and the prevention of UV-induced immunosuppression by IL-12.

IL-15 is involved in lymphocyte homeostasis. To investigate the role of IL-15 in the skin in vivo, mice were generated that overexpress IL-15 in keratinocytes, resulting in increased IL-15 protein levels in the skin but not elevated IL-15 serum concentrations. Keratin 14 (K14)-IL-15 transgenic (tg) mice showed increased contact hypersensitivity (CHS) responses. Transfer of primed wild-type (wt) and tg T cells into naive wt or tg recipients indicated that skin-derived IL-15 enhanced the induction but not the elicitation phase of CHS. Tg mice could be sensitized even by suboptimal hapten concentrations. Accordingly, Langerhans cells (LC) from tg skin were identified as potent allostimulators, suggesting the involvement of IL-15-stimulated LC in the induction of adaptive immunity. Overexpression of IL-15 also strengthened innate immunity since tg mice infected with human HSV type I developed significantly smaller HSV skin lesions. In addition, tg mice resisted re-infection with HSV more effectively than wt mice did, which was associated with an elevated anti-HSV Ab production. Accordingly, injection of serum from re-infected tg mice protected naive recipients significantly from epicutaneous HSV infection, indicating that anti-HSV Ab produced by tg mice play an important role in resistance in vivo. Together, our results show that overexpression of IL-15 in the epidermis enhances both innate and adaptive cutaneous immunity.

CD4+CD25+ regulatory T cells (Treg cells) control immune responsiveness to a large variety of antigens. The isolation and therapeutic manipulation of Treg cells requires the use of reliable surface receptors that are selectively up-regulated in Treg cells. On the basis of global gene expression studies, we identified neuropilin-1 (Nrp1) as a specific surface marker for CD4+CD25+ Treg cells. Nrp1, a receptor involved in axon guidance, angiogenesis, and the activation of T cells, is constitutively expressed on the surface of CD4+CD25+ Treg cells independently of their activation status. In contrast, Nrp1 expression is down-regulated in naive CD4+CD25- T cells after TCR stimulation. Furthermore, CD4+Nrp1(high) T cells express high levels of Foxp3 and suppress CD4+CD25- T cells. Thus, Nrp1 constitutes a useful surface marker to distinguish Treg cells from both naive and recently activated CD4+CD25+ non-regulatory T cells.

Epicutaneous application of haptens to UV-exposed skin induces hapten-specific tolerance. This is mediated via regulatory T cells (Tr), as i.v. injection of T cells from UV-tolerized mice into naive animals renders the recipients unresponsive to the respective hapten. However, when UV-induced Tr are injected i.v. into sensitized mice, contact hypersensitivity (CHS) is not suppressed, suggesting that Tr inhibit the induction, but not the elicitation, of CHS and are inferior to T effector cells. As sensitization takes place in the lymph nodes, but elicitation occurs in the area of challenge, we postulated that Tr injected i.v. locate to the lymph nodes and not to the periphery and therefore only suppress the induction, not the elicitation, of CHS. Indeed, i.v. injection of Tr into sensitized mice did not inhibit CHS, although injection of Tr into the ears of sensitized mice suppressed the challenge. Inhibition was hapten specific, as injection of dinitrofluorobenzene (DNFB)-specific Tr into the ears of oxazolone (OXA)-sensitized mice did not affect challenge with OXA. However, when ears of OXA-sensitized mice were injected with DNFB-specific Tr and painted with DNFB before OXA challenge, CHS was suppressed. Inhibition correlated with the local expression of IL-10. Depletion studies and FACS analysis revealed that Tr express the lymph node-homing receptor L-selectin, but not the ligands for the skin-homing receptors E- and P-selectin, suggesting that UV-induced Tr, although able to inhibit T effector cells, do not suppress the elicitation of CHS upon i.v. injection, because they obviously do not migrate into the skin.

Lichen planus (LP) is an inflammatory skin disorder with a wide range of clinical appearances. The treatment of disseminated and especially erosive forms of LP is often difficult and disappointing. Activated T cells are important in the pathogenesis of LP as indicated by the dermal lymphocytic infiltrate leading to keratinocyte destruction and lesion formation. Similar histologic findings are present in graft-versus-host disease. Since T cells are key players in the development of both disorders and mycophenolate mofetil has been successfully introduced in the treatment of graft-versus-host disease, we have examined the therapeutic potential of this agent in 3 patients suffering from disseminated and erosive LP. Mycophenolate mofetil was well tolerated and induced complete remission in 2 patients, and substantial improvement in the third patient.

GM-CSF takes part in the cytokine network regulating the metabolism of extracellular matrix (ECM) during atherogenesis. Since data also point to an effect of GM-CSF on the vascular ECM in general, the vascular collagenous matrix was studied in wild-type and GM-CSF-deficient mice. Histological examination revealed a disorganized vascular ECM in GM-CSF-deficient mice involving the collagenous matrix and elastic fiber system. As shown by electron microscopy, collagen bundles were disrupted and reduced. The diameter of fibrils varied widely. mRNA expression of collagens and related molecules was studied. Fibrillar collagens were markedly reduced, alpha1(I)procollagen to 16.5% of control levels alpha1(III)procollagen was abolished whereas the expression level of network-forming alpha1(VIII)procollagen was not altered. As shown by in situ hybridization, the number of collagen-expressing cells was reduced. Matrix metalloproteinases and their inhibitor 1 were not affected by GM-CSF deficiency. Our studies demonstrate that GM-CSF plays a major role in the cytokine network regulating the metabolism of vascular collagens. GM-CSF deficiency leads to an altered composition of the vascular collagenous matrix, i.e., reduced amount of fibrillar collagen, altered ratio of fibrillar and network-forming collagen, and failures in the fibrillogenesis. We suggest that GM-CSF is a basic requirement for the maintenance of vessel wall integrity and resilience.

IL-10 is a pleiotropic cytokine that inhibits several immune parameters, including Th1 cell-mediated immune responses, antigen presentation, and antigen-specific T cell proliferation. Recent data implicate IL-10 as a mediator of suppression of cell-mediated immunity induced by exposure to UVB radiation (280-320 nm). To investigate the effects of IL-10 on the cutaneous immune system, we engineered transgenic mice that overexpress viral IL-10 (vIL-10) in the epidermis. vIL-10 transgenic mice demonstrated a reduced number of I-A(+) epidermal and dermal cells and fewer I-A(+) hapten-bearing cells in regional lymph nodes after hapten painting of the skin. Reduced CD80 and CD86 expression by I-A(+) epidermal cells was also observed. vIL-10 transgenic mice demonstrated a smaller delayed-type hypersensitivity response to allogeneic cells upon challenge but had normal contact hypersensitivity to an epicutaneously applied hapten. Fresh epidermal cells from vIL-10 transgenic mice showed a decreased ability to stimulate allogeneic T cell proliferation, as did splenocytes. Additionally, chronic exposure of mice to UVB radiation led to the development of fewer skin tumors in vIL-10 mice than in WT controls, and vIL-10 transgenic mice had increased splenic NK cell activity against YAC-1targets. These findings support the concept that IL-10 is an important regulator of cutaneous immune function.

Autoimmune disorders play an increasing role in public health, especially in light of the fact of the growing aged population, which primarily develop such diseases. A clear understanding of the mechanisms leading to the development of autoimmune responses and finally to autoimmune disease does not exist. Autoimmunity is characterized by the presence of autoantibodies and/or autoreactive T cells and the corresponding organ manifestation. Following the discovery of autoreactive T cells found in the periphery of mice and humans, the old immunological concept that autoreactive T cells are completely deleted in the thymus during evolution has been revised in recent years. Although antigen-presenting cells and particularly dendritic cells are known to play an important role in the regulation of immune responses and the activation of T cells, recent evidence suggests that the role of dendritic cells in the development of autoimmunity has been underestimated previously. This article aims to give a general overview on the basic immunological principles involved and gives a short review of the current literature on the functional relevance of dendritic cells in various human and murine autoimmune disorders.

The mechanisms underlying UV-induced immunosuppression and the development of UV-induced skin cancer have been intensively investigated for decades. In particular, UV-induced DNA damage and UV-induced suppression of cellular immune responses were analyzed in great detail. During this time, several cellular and genetic pathways were identified, that are involved in photoimmunology and photocarcinogenesis. However, the direct effects of the complex UV-induced pathways on immunosuppression or on cutaneous tumor generation in vivo have not been able to be characterized with certainty so far. With the increasing availability of mutant mice that lack or overexpress certain genes, more information can be obtained with respect to the functional importance of individual gene products and the signaling pathways involved in UV-mediated immunomodulation and cancer development. This article is an overview of the results of UV-induced immunosuppression and photocarcinogenesis experiments obtained in different mutant mice.

Within the last two decades phototherapy has turned out to be a major therapeutic strategy in dermatology and thus has significantly influenced the treatment of many dermatoses. The goals of therapeutic photomedicine are the suppression of ongoing disease processes and, more importantly, the prevention, modulation, or abrogation of pathogenic mechanisms causing the disease. Therapeutic photomedicine has been largely empirical and most of it is still empirical today. However, parts of it are already based on the advances in photoimmunology and molecular biology. Although, we are far from a detailed understanding of the mechanisms underlying phototherapy, there is increasing evidence that phototherapy acts via modulation of the immune system. Most of the effects of both ambient and therapeutic ultraviolet radiation are immunosuppressive in nature.

Beta2 integrins are of critical importance for leukocyte extravasation through vascular endothelia and for T cell activation. To elucidate the role of beta2 integrins in T cell-mediated immune responses, allergic contact dermatitis (ACD), irritant dermatitis, and delayed-type hypersensitivity (DTH) were assessed in mice lacking the beta2 integrin subunit, CD18. ACD and DTH responses, but not edema formation, were severely suppressed in CD18(-/-) mice. Extravasation of CD18(-/-) T cells into eczematous skin lesions was greatly impaired, whereas migration of Langerhans cell precursors and dendritic cells was normal in CD18(-/-) mice. CD18(-/-)lymph nodes (LNs) contained an abnormal population of CD3(-)CD44(high) lymphocytes and showed evidence of widespread T cell activation. T cells from regional LNs of sensitized CD18(-/-) mice proliferated in response to hapten challenge, and subcutaneous injection of sensitized syngeneic LN cells directly into ears of hapten-challenged naive recipients restored the defective ACD in CD18(-/-) mice, suggesting that CD18 is not required for priming of naive T cells but is indispensable for T cell extravasation. Thus, a dysfunction of T cells, in addition to granulocytes, may contribute to the pathophysiology of leukocyte adhesion deficiency type I, which arises from mutations in the human CD18 gene.

UV radiation induces skin cancer primarily by its DNA-damaging properties, but also by its capacity to suppress the immune system. The photoisomer of urocanic acid (UCA), cis-UCA, is an important mediator of UV-induced immunosuppression and is involved in the inhibition of tumor immunity. The immunomodulatory cytokine IL-12 is known to counteract many of the immunosuppressive effects of UV radiation, including UV-induced immune tolerance. In this study, we addressed whether IL-12 also reverts the immunosuppressive activities of cis-UCA. Cis-UCA inhibits the ability of Langerhans cells to present tumor Ags for primary and secondary tumor immune responses. IL-12 treatment completely prevented the suppression by cis-UCA. IL-12 also protected mice from cis-UCA-induced suppression of contact hypersensitivity responses. To study the effects of cis-UCA on Ag-processing and Ag-presenting function in vitro, Langerhans cells were treated with UCA isomers and incubated with OVA or OVA peptide(323-339) before exposure to OVA-specific transgenic T cells. Cis-, but not trans-UCA suppressed Ag presentation, which was completely reversed upon addition of IL-12. Since these findings suggest that cis-UCA may play an important role in photocarcinogenesis by inhibiting a tumor immune response, mice were chronically UVB irradiated to induce skin cancer. Whereas all mice in the control groups developed tumors, mice treated with a mAb with specificity for cis-UCA showed a significantly reduced tumor incidence. These data strongly indicate the importance of cis-UCA during photocarcinogenesis and support the concept of counteracting cis-UCA as an alternative strategy to prevent UV-induced skin cancer, possibly via the application of IL-12.

CD40-CD40 ligand (L) interactions play a pivotal role in immune-mediated inflammatory responses via the activation of antigen-presenting cells (APCs). To investigate the effects of continuous activation of resident tissue APCs, in this case the Langerhans cells (LCs) of the skin, CD40L expression was targeted to the basal keratinocytes of the epidermis of mice using the keratin-14 promoter. Approximately 80% of the transgenic (Tg) mice spontaneously developed dermatitis on the ears, face, tail, and/or paws. Compared with littermates, Tgs had a >90% decrease in epidermal LCs yet increased numbers within the dermis suggestive of enhanced emigration of CD40-activated LCs. Tgs also displayed massive regional lymphadenopathy with increased numbers of dendritic cells and B cells. Moreover, a decrease in IgM and an increase in IgG1/IgG2a/IgG2b/IgE serum concentrations was detectable. Screening for autoantibodies revealed the presence of antinuclear antibodies and anti-dsDNA antibodies implicative of systemic autoimmunity. Accordingly, renal Ig deposits, proteinuria, and lung fibrosis were observed. Adoptive transfer of T cells from Tgs to nonTg recipients evoked the development of skin lesions similar to those found in the Tgs. Dermatitis also developed in B cell-deficient CD40L Tg mice. These findings suggest that in situ activation of LCs by CD40L in the skin not only leads to chronic inflammatory dermatitis but also to systemic mixed-connective-tissue-like autoimmune disorders, possibly by breaking immune tolerance against the skin.

The antiapoptotic protein bcl-2 is found up-regulated in a number of malignant and premalignant skin conditions of keratinocyte origin, but in normal skin, it is expressed at low levels only in interfollicular epidermis. To investigate whether unregulated bcl-2 expression could affect the incidence of epidermal tumors, we have generated a mouse line that over-expresses human bcl-2 in the basal layer of epidermis under the control of the human keratin 14 promoter. These mice were subjected to both UVB photocarcinogenesis and classical two-stage chemical carcinogenesis. Although transgenic bcl-2 in these mice reduces the formation of sunburn cells after short-term UVB irradiation, chronically UVB irradiated K14/bcl-2 mice were protected against tumor development, because transgenic mice developed tumors much later and at a significantly lower frequency than controls. Immunohistochemical analyses of the UVB-induced tumors revealed no significant differences in the degree of inflammatory cell infiltrates. When either K14/bcl-2 mice or F(1) progeny of matings with mice expressing an activated Ha-ras oncogene (K14/bcl-2/ras) were treated with 9,10-dimethyl-1,2-benzanthracene/phorbol 12-myristate 13-acetate, the latency of first papilloma appearance was the same in transgenic mice and controls, but further papillomas developed more slowly in the mutant mice. Moreover, the K14/bcl-2/ras mice developed far fewer albeit larger tumors/mouse than did the ras/+ controls. The rate of conversion to malignant carcinomas, the carcinoma grade, and the frequency of lymph node metastases were not significantly different between mutants and controls. We conclude that, despite its antiapoptotic function, bcl-2, overexpressed in basal epidermal keratinocytes, exerts a paradoxical retardation on the development of skin tumors induced by chemical carcinogens and particularly by UVB.

The immunosuppressive drug, mycophenolate mofetil (MMF), has been successfully introduced in allogeneic transplantation medicine and, more recently, in the treatment of autoimmune skin disorders. MMF inhibits lymphocyte proliferation via a blockade of the enzyme inosine 5'-monophosphate dehydrogenase, an enzyme on which lymphocytes solely depend to generate the purines necessary for DNA/RNA synthesis. To investigate the effects of MMF on cutaneous immune responses, a murine model of contact hypersensitivity (CHS) was used, with oxazolone or trinitrochlorobenzene as a contact allergen. Compared with the respective vehicle, i.p. applied MMF significantly inhibited the elicitation and, surprisingly, the induction of CHS responses. This prompted further studies into the effects of MMF on Ag presentation. Bone marrow-derived dendritic cells (DC) were cultured with GM-CSF and IL-4 in the presence of MMF and were tested for their Ag-presenting capacity. Sensitization and elicitation of CHS and delayed-type hypersensitivity responses by s. c. injected haptenated DC were reduced upon preincubation of DC with MMF. CHS responses were not impaired upon resensitization, indicating that MMF does not induce hapten-specific immunotolerance. In addition, MMF decreased the ability of DC to stimulate allogeneic T cells in MLR assays. Accordingly, flow cytometric analyses revealed a dose-dependent reduction of the expression of CD40, CD80, CD86, I-A, and ICAM-1 on DC with a concurrent reduction of IL-12 production. These data suggest that MMF, in addition to affecting T lymphocytes, directly affects APC, resulting in an impairment of immune responses. They furthermore point to a possible role of inosine 5'-monophosphate dehydrogenase in the maturation of DC.

Hapten sensitization through UV-exposed skin induces hapten-specific tolerance that can be adoptively transferred by injecting T lymphocytes into naive recipients. The exact phenotype of T cells responsible for inhibiting the immune response and their mode of action remain unclear. Evidence exists that CTLA-4 negatively regulates T cell activation. We addressed whether CTLA-4 is involved in the transfer of UV-induced tolerance. Injection of lymph node cells from mice that were sensitized with dinitrofluorobenzene (DNFB) through UV-irradiated skin inhibited induction of contact hypersensitivity against DNFB in the recipient animals. When CTLA-4+ cells were depleted, transfer of suppression was lost. Likewise, significantly fewer lymphocytes enriched for CTLA-4+ cells were necessary to transfer suppression than unfractionated cells. Expression of CTLA-4 appears to be functionally relevant, since in vivo injection of a blocking anti-CTLA-4 Ab was able to break UV-induced tolerance and inhibited transfer of suppression. Upon stimulation with dendritic cells in the presence of the water-soluble DNFB analogue, DNBS, CTLA-4+ T cells from DNFB-tolerized mice secreted high levels of IL-10, TGF-beta, and IFN-gamma; low levels of IL-2; and no IL-4, resembling the cytokine pattern of T regulatory 1 cells. Ab blocking of CTLA-4 resulted in inhibition of IL-10 release. Accordingly, transfer of tolerance was not observed when recipients were treated with an anti-IL-10 Ab. Hence we propose that T cells, possibly of the T regulatory 1 type, transfer UV-mediated suppression through the release of IL-10. Activation of CTLA-4 appears to be important in this process.

Several phenotypes of antigen-presenting cells are present in the dermis, where they presumably function to present encountered antigens for immune responses. This study examined the ability of dermal antigen-presenting cells to present tumor-associated antigens for the induction of in vivo antitumor immunity. Total murine dermal cells were exposed either to medium alone or to medium containing tumor-associated antigens from S1509a tumor cells. Subsequently, dermal cells were injected subcutaneously at weekly intervals into naïve mice for a total of three immunizations. One week following the final immunization, mice were challenged with living tumor cells. In these experiments, dermal cells pulsed with tumor-associated antigens induced protective immunity to tumor growth. Dermal cells exposed to tumor-associated antigens were also able to elicit delayed-type hypersensitivity after footpad injection into mice previously immunized against S1509a tumor cells. The ability to present tumor-associated antigens for both induction of antitumor immunity and elicitation of delayed-type hypersensitivity was dependent on I-A+ cells and was genetically restricted. Finally, dermal cells tended towards eliciting a greater antitumor delayed-type hypersensitivity response than epidermal cells. These results show that the murine dermis contains antigen-presenting cells capable of processing S1509a tumor antigens for the generation of protective antitumor immunity in vivo.

Induction of tolerance by subsequent UV exposures is the most effective therapy for solar urticaria; however, it is time-consuming and takes a long time until protection is achieved. Three patients with solar urticaria were exposed to multiple UVA irradiations at 1-hour intervals per day. With this rush hardening regimen, protection was achieved within 3 days.

Immunosuppression by UV light contributes significantly to the induction of skin cancer by suppressing the cell-mediated immune responses which control the development of carcinogenesis. The B7/CD28-CTLA-4 signaling pathway provides costimulatory signals essential for Ag-specific T cell activation. To investigate the role of this pathway in photocarcinogenesis, we utilized transgenic (Tg) mice which constitutively express CTLA-4Ig, a high-affinity CD28/CTLA-4 antagonist that binds to both B7-1 and B7-2. The transgene is driven by a skin-specific promoter yielding high levels of CTLA-4Ig in the skin and serum. Chronic UV exposure of CTLA-4Ig Tg mice resulted in significantly reduced numbers of skin tumors, when compared to control mice. In addition, Tg mice were resistant to UV-induced suppression of delayed-type hypersensitivity responses to alloantigens. Most importantly, upon stimulation with mitogens and alloantigens, T cells isolated from CTLA-4Ig Tg mice produced significantly less IL-4 but more IFN-gamma compared to control T cells, suggesting an impaired Th2 response and a relative increase of Th1-type immunity. Together, these data show that overall B7 engagement directs immune responses toward the Th2 pathway. Moreover, they point out the crucial role of Th1 immune reactions in the protection against photocarcinogenesis.

Background: The perception of pruritus is modified by endogenous opiates via central opiate receptors in a histamine-independent manner., Objective: The aim of this pilot study was to evaluate the efficacy and safety of naltrexone, an orally active opiate antagonist, in the treatment of severe, otherwise intractable pruritus of different origin in an open-label clinical trial., Methods: A total of 50 patients with pruritus caused by internal diseases, hydroxyethyl starch, contact with water, cutaneous lymphoma, atopic dermatitis, xerosis cutis, macular amyloidosis, psoriasis, and other skin disorders as well as with pruritus of unknown origin were randomly selected to receive naltrexone 50 mg daily. The pruritus intensity was rated by the patients before and during therapy in a visual analogue scale., Results: A significant therapeutic response was achieved in 35 of the 50 patients within 1 week (confidence limits of 0.55 and 0.82 at a confidence level of 0. 95). Naltrexone was of high antipruritic effect in 9 of 17 cases of prurigo nodularis and contributed to healing of the skin lesions. Tachyphylaxis was infrequent (6/50), occurred late, and could be counterbalanced by raising the dosage in 2 patients. Adverse drug effects were restricted to the first 2 weeks of treatment and included nausea (11/50), fatigue (3/50), dizziness, heartburn, and diarrhea (1/50 each)., Conclusion: The study suggests that oral opiate antagonists might be a well-tolerated and effective therapy for pruritic symptoms in many diseases.

Ultraviolet light (UV) represents one of the most relevant environmental factors influencing humans, especially with regard to its hazardous health effects, which include premature skin aging, skin cancer, and exacerbation of infectious diseases. Several of these effects are mediated by the immunosuppressive properties of UV. UV can compromise the immune system in several ways, e.g., by affecting the function of antigen-presenting cells, inducing the release of cytokines, and modulating the expression of surface molecules. Recently a link between UV-induced immunosuppression and apoptosis was recognized. In the following, the basic mechanisms underlying UV-induced immunosuppression will be discussed.

We report the third case of lipodystrophia centrifugalis abdominalis outside East Asia. A 4-year-old Caucasian girl developed an area of bluish erythema on the left side of the lower abdomen which spread centrifugally to the umbilical and inguinal areas with depression of the skin resulting from the loss of subcutaneous fat, surrounded by an erythematous border. This unusual skin disease was characterized by clinical and histological examination. Laboratory tests revealed a partial IgA deficiency, antinuclear antibodies and IgG antibodies against gliadin.

Embolia cutis medicamentosa (Nicolau Syndrome) is a very rare complication of intramuscular injections which presents with extensive necrosis of the injected skin area. Intra-arteria and/or para-arterial injections after prior perforation of certain vessels are discussed as possible pathogenetic mechanisms. We describe the occurrence of embolia cutis medicamentosa after intra-articular injections into the knee.

Thy-1 is a cell surface glycoprotein expressed mainly on brain and lymphoid tissue. Although the functions of Thy-1 are incompletely understood, evidence exists that Thy-1 participates in T cell activation. To examine the functional role of Thy-1 in cutaneous immune responses in vivo, Thy-1 gene-targeted mice (Thy-1-/-) and wild-type mice (Thy-1+/+) were immunized with the hapten oxazolone. After challenge with oxazolone, contact hypersensitivity responses in Thy-1-/- mice were reduced by 25% compared with Thy-1+/+ mice. Likewise, irritant dermatitis induced by croton oil was also decreased. In addition, Thy-1-/- mice showed a significantly reduced delayed-type hypersensitivity response after injection of allogeneic spleen cells into the hind footpads of allosensitized animals when compared with Thy-1+/+ mice. Moreover, proliferative responses to immobilized anti-CD3 were decreased in peripheral Thy-1-/- lymphocytes; this decrease was associated with a significantly reduced intracellular Ca2+ influx and protein tyrosine phosphorylation, indicating impairment of early lymphocyte activation. In contrast, the T cell proliferation induced by mitogens was normal, suggesting that Thy-1 expression weakly contributes to TCR-mediated T cell activation. Epidermal Langerhans cells and bone marrow-derived dendritic cells from Thy-1-/- mice exhibited a normal expression of costimulatory surface molecules as well as an unaltered ability to stimulate allogeneic T cells. Taken together, these findings demonstrate that a lack of Thy-1 expression does not generally compromise the immune system; however, Thy-1 expression may be involved in the fine-tuning of T cell-mediated immune responses.

IL-1 exists in two forms, termed IL-1alpha and IL-1beta, which exert similar effects in a number of biologic models. Recently, there have been reports of some differences in the activities of these two species in some systems. To address this issue with regard to Langerhans cells, Langerhans cell-enriched preparations of epidermal cells were treated with either IL-1alpha or IL-1beta before pulsing with S1509a tumor-associated antigens and subsequent use for immunization of naive mice to S1509a. While epidermal cells treated with 100 U IL-1beta per ml were able to induce protective tumor immunity (as indicated by the rejection of a subsequent tumor challenge with viable S1509a tumor cells), epidermal cells treated with 100 U IL-1alpha per ml failed to confer protective immunity. At 1000 U per ml, IL-1beta also inhibited the ability of epidermal cells to induce tumor immunity. To investigate the effects of the two IL-1 forms on elicitation of tumor immunity, naive mice were immunized against the S1509a tumor by s.c. injection of dead S1509a cells. Epidermal cells enriched for Langerhans cells were treated with either 100 U IL-1alpha or IL-1beta per ml before tumor-associated antigens-pulsing. Epidermal cells were then washed and injected into a hind footpad of tumor immune mice and 24 h footpad swelling was assessed as a measure of delayed-type hypersensitivity. Exposure to IL-1alpha led to suppressed elicitation of delayed-type hypersensitivity, whereas IL-1beta treated epidermal cells elicited a normal (100 U per ml) or enhanced (1000 U per ml) level of delayed-type hypersensitivity. Previous experiments indicated that the suppressive effects of IL-1alpha on induction of immunity may be mediated by TNF alpha. Therefore, the ability of IL-1alpha or IL-1beta to induce epidermal cell production of TNF alpha was assessed. IL-1alpha induced epidermal cells to secrete significantly higher amounts of TNF alpha protein compared with stimulation with IL-1beta. IL-1alpha and IL-1beta appear to differentially regulate epidermal cell antigen presenting capability.

The in vivo functions of interleukin-3 (IL-3) were investigated by generating IL-3-deficient mice. Although hematopoiesis was unimpaired in homozygous mutant animals, contact hypersensitivity reactions were compromised. IL-3 was required for efficient priming of hapten-specific contact hypersensitivity responses, but was dispensable for T-cell-dependent sensitization to tumor cells. These findings reveal a critical role for IL-3 in some forms of delayed-type hypersensitivity.

Mycophenolate mofetil (MMF) is a new immunosuppressive drug which non-competitively and reversibly blocks the de novo synthesis of guanine nucleotides required for DNA and RNA synthesis during T- and B-cell proliferation. This induces a selective inhibition of lymphocyte proliferation. Thus MMF is currently used to prolong graft survival in renal transplant patients. In this communication we describe the first case of a man with severe psoriasis treated successfully with oral MMF without short-term side-effects. The psoriasis area and severity index score decreased during therapy (5 weeks) from 22.0 to 11.4. Thus MMF appears to be an effective therapeutic alternative in the treatment of severe psoriasis.

Urocanic acid (UCA) accumulates in the epidermis after deamination of histidine. UCA isomerizes from the trans to the cis form upon exposure to environmental UV radiation. Cis-UCA is immunosuppressive in several models. Topically applied cis-UCA was reported to enhance the cutaneous tumor yield in chronically UV-irradiated mice, suggesting involvement of cis-UCA in photocarcinogenesis. Since Langerhans cells (LC) are capable of presenting tumor-associated Ags (TAA) for primary and secondary tumor-immune responses, we examined the effects of trans- and cis-UCA on LC tumor Ag presentation in a model of immunity to the S1509a spindle cell tumor (H-2a). In this system, induction of immunity requires exposure of LC to granulocyte-macrophage CSF. Naive CAF1 (H-2(a/d)) mice were immunized against S1509a by injection with granulocyte-macrophage CSF-exposed and TAA-pulsed epidermal cells (EC), as assessed by growth inhibition of inoculated tumor cells. Incubation of EC in cis-, but not trans-UCA completely inhibited Ag presentation in this system. Neither histamine antagonists nor indomethacin reversed these effects of cis-UCA. The ability of trans- and cis-UCA to modulate EC presentation of TAA for secondary immune responses was also examined. EC were pulsed with TAA in vitro and then injected into hind footpads of tumor-immune mice. After 24 h, footpad swelling was assessed as a measure of delayed-type hypersensitivity. Incubation with cis-, but again not trans-UCA before TAA exposure significantly inhibited elicitation of delayed-type hypersensitivity. These data indicate that cis-UCA may be an important regulator of LC Ag-presenting function in tumor-immune responses, and thus may play a role in photocarcinogenesis.

Calcitonin gene-related peptide (CGRP) inhibits antigen presentation by Langerhans cells (LC) and macrophages, and LC are anatomically associated with CGRP-containing epidermal nerves. To determine whether CGRP may produce some of its functional effects through regulation of cytokine expression, we utilized enzyme-linked immunosorbent assay (ELISA) of conditioned supernatants to examine production of interleukin (IL)-10 and IL-1 beta protein in the LC-like cell line XS52 as well as the reverse transcriptase-polymerase chain reaction (RT-PCR) to examine levels of mRNA for IL-10, IL-1 beta, and the 40-kDa subunit (p40) of IL-12. CGRP augmented the lipopolysaccharide (LPS) and granulocyte-macrophage colony-stimulating factor (GM-CSF) -induced release of IL-10 protein and the induced expression of IL-10 mRNA in these cells. However, it suppressed the induction of release of IL-1 beta protein and the induction of mRNA for IL-12 p40 and IL-1 beta by LPS and GM-CSF. Regulation of cytokine expression in peritoneal macrophages was also examined. By ELISA, the LPS-induced expression of IL-10 was augmented by CGRP, whereas the induction of IL-1 beta was suppressed. Northern analysis demonstrated augmentation of LPS-induced IL-10 mRNA levels and inhibition of LPS-induced IL-1 beta mRNA by CGRP. CGRP inhibited the LPS-induced induction of IL-12 mRNA as assessed by RT-PCR. Up-regulation of B7-2 expression by LPS and GM-CSF was suppressed by CGRP in both XS52 cells and macrophages, as previously reported. This suppression, however, could be abrogated by co-culture with neutralizing antibodies to IL-10. Furthermore, the presence of neutralizing antibodies to IL-10 during exposure of epidermal cells (EC) to CGRP prevented the CGRP-mediated suppression of EC presentation of tumor-associated antigens (from the S1509a spindle cell carcinoma) for elicitation of delayed-type hypersensitivity in S1509a-immune mice. These data suggest that suppression of antigen-presenting function by CGRP is mediated, at least in part, by changes in cytokine expression that favor less robust antigen presentation for cell-mediated immunity.