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Insulin is a key autoantigen in Type 1 Diabetes (T1D), targeted by both T and B cells. Therefore, understanding insulin-specific T:B cell interactions is important. We have previously reported an insulin-reactive CD4+ T cell, (designated 2H6). Unlike other insulin-reactive T cells, 2H6 cells protect non-obese diabetic (NOD) mice from T1D development, mediated by TGFβ. To investigate insulin-specific T:B cell interactions, we bred 2H6αβ T cell receptor transgenic NOD mice (2H6) with the insulin-reactive B cell receptor transgenic NOD mice (VH125), generating 2H6VH125 NOD mice. Similar to 2H6 mice, 2H6VH125 mice are protected from T1D development. Interestingly, VH125 B cells did not alter the phenotype of 2H6 T cells; however, 2H6 T cells significantly altered the VH125 B cells by reducing the insulin-reactive non-germinal center (GC) and GC B cells, as well as MHC and costimulatory molecule expression on the B cells. Furthermore, the B cells in 2H6VH125 NOD mice exhibited increased non-insulin-specific and a class switched IgG isotype, which can be recapitulated in vivo in Rag-deficient NOD mice by adoptive transfer. In vitro, VH125 B cells from 2H6VH125 mice suppressed the proliferation of 2H6 T cells to insulin antigen but enhanced TGFβ secretion by 2H6 T cells from 2H6VH125 mice compared to 2H6 mice. In summary, our data showed that 2H6 CD4+ T cells alter the phenotype and function of insulin-reactive B cells from pathogenic to tolerogenic cells. In turn, VH125 B cells also modulate the function of the 2H6 T cells. Thus, promoting the interactions between antigen-specific regulatory T cells and B cells may lead to protection from T1D.

Background\ud Genetic background influences allergic immune responses to environmental stimuli. Non‐obese diabetic (NOD) mice are highly susceptible to environmental stimuli. Little is known about the interaction of autoimmune genetic factors with innate immunity in allergies, especially skin hypersensitivity.\ud \ud Objectives\ud To study the interplay of innate immunity and autoimmune genetic factors in contact hypersensitivity (CHS) by using various innate immunity‐deficient NOD mice.\ud \ud Methods\ud Toll‐like receptor (TLR) 2‐deficient, TLR9‐deficient and MyD88‐deficient NOD mice were used to investigate CHS. The cellular mechanism was determined by flow cytometry in vitro and adoptive cell transfer in vivo. To investigate the role of MyD88 in dendritic cells (DCs) in CHS, we also used CD11cMyD88+ MyD88−/− NOD mice, in which MyD88 is expressed only in CD11c+ cells.\ud \ud Results\ud We found that innate immunity negatively regulates CHS, as innate immunity‐deficient NOD mice developed exacerbated CHS accompanied by increased numbers of skin‐migrating CD11c+ DCs expressing higher levels of major histocompatibility complex II and CD80. Moreover, MyD88−/− NOD mice had increased numbers of CD11c+ CD207− CD103+ DCs and activated T effector cells in the skin‐draining lymph nodes. Strikingly, re‐expression of MyD88 in CD11c+ DCs (CD11cMyD88+ MyD88−/− NOD mice) restored hyper‐CHS to a normal level in MyD88−/− NOD mice.\ud Conclusion\ud Our results suggest that the autoimmune‐prone NOD genetic background aggravates CHS regulated by innate immunity, through DCs and T effector cells.

We propose that there is a special B-1a B cell subset ("sB-1a" cells) that mediates linked processes very early after immunization to initiate cutaneous contact sensitivity (CS), delayed-type hypersensitivity (DTH), and immune resistance to pneumococcal pneumonia. Our published data indicate that in CS and DTH, these initiating processes are required for elicitation of the delayed onset and late-occurring classical T cell-mediated responses. sB-1a cells resemble memory B2 cells, as they are stimulated within 1 h of immunization and depend on T helper cytokines-uniquely IL-4 from hepatic iNKT cells--for activation and rapid migration from the peritoneal cavity to the spleen to secrete IgM antibody (Ab) and Ab-derived free light chains (FLCs) by only 1 day after immunization. Unlike conventional B-1a (cB-1a) cell-produced IgM natural Ab, IgM Ab produced by sB-1a cells has high Ag affinity owing to immunoglobulin V-region mutations induced by activation-induced cytidine deaminase (AID). The dominant cB-1a cells are increased in immunized AID-deficient mice but do not mediate initiation, CS, or pneumonia resistance because natural Ab has relatively low Ag affinity because of unmutated germ-line V regions. In CS and DTH, sB-1a IgM Ag affinity is sufficiently high to mediate complement activation for generation of C5a that, together with vasoactive mediators such as TNF-α released by FLC-sensitized mast cells, activate local endothelium for extravascular recruitment of effector T cells. We conclude by discussing the possibility of functional sB-1 cells in humans.

Background Oral enrofloxacin treatment altered the gut microbiome promoting anti-inflammatory bacteria. The dysbiosis promotes regulatory cell induction in the intestines and in the periphery, which suppresses contact sensitivity. Bacterial-derived signals promote regulatory cell induction both directly and indirectly by influencing the phenotype of dendritic cells (DC). Methods Oral treatment with broad-spectrum antibiotic enrofloxacin was used to evaluate how gut flora perturbation shapes the immune response in the gut and the periphery. Results Enrofloxacin-induced dysbiosis creates an anti-inflammatory environment characterized by increased IL-10 concentration in the gut lumen and tissues. The production of IFN-γ and IL-17A did not change. Oral enrofloxacin treatment skewed the profile of the immune response towards an anti-inflammatory phenotype locally in small intestinal Peyer’s Patches (PP) and systematically in the spleen (SPL). Enrofloxacin administration changed immune response in PP by increasing TGF-β secretion from an increased percentage of TGF-β-producing. In the SPL, enrofloxacin treatment increased the secretion of TGF-β and IL-10 and decreased the secretion of IL-17A and IFN-γ. The shift in cytokine profile correlated with a higher percentage of latency-associated peptide and IL-10-producing cells and a decreased percentage of IFN-γ-producing T cells. This anti-inflammatory immune response in the PP and SPL promoted a higher frequency of tolerogenic DC. Conclusion Our data indicate that two-week enrofloxacin treatment induces dysbiosis, skews immune response towards an anti-inflammatory phenotype, and elevates secretion of TGF-β and IL-10 in the intestines and periphery. Additionally, we observed higher frequencies of tolerogenic DC, characterized by CD11b and IL-10 expression, which are known inducers of Treg cells.

Background Subcutaneous allergen-specific immunotherapy is a standard route for the immunotherapy of allergic diseases. It modulates the course of allergy and can generate long-term remission. However, subcutaneous allergen-specific immunotherapy can also induce anaphylaxis in some patients, and therefore additional routes of administration should be investigated to improve the safety and tolerability of immunotherapy. Objective We sought to determine whether epicutaneous treatment with antigen in the presence of a Toll-like receptor 9 agonist can suppress T H 2-mediated responses in an antigen-specific manner. Methods Epicutaneous immunization was performed by applying a skin patch soaked with ovalbumin (OVA) plus CpG, and its suppressor activity was determined by using the mouse model of atopic dermatitis. Finally, adoptive cell transfers were implemented to characterize the regulatory cells that are induced by epicutaneous immunization. Results Epicutaneous immunization with OVA and CpG reduces the production of OVA-specific IgE and increases the synthesis of OVA-specific IgG 2a antibodies in an antigen-specific manner. Moreover, eosinophil peroxidase activity in the skin and production of IL-4, IL-5, IL-10, and IL-13 are suppressed. The observed reduction of IgE synthesis is transferable with T-cell receptor (TCR) αβ + CD4 + CD25 − cells, whereas IgG 2a production is dependent on both TCRαβ + and TCRγδ + T cells. Further experiments show that the described phenomenon is myeloid differentiation primary response 88, IFN-γ, and IL-17A dependent. Finally, the results suggest that epicutaneous immunization with OVA and CpG decreases the synthesis of OVA-specific IgE and skin eosinophil peroxidase activity in mice with ongoing skin allergy. Conclusion Epicutaneous application of protein antigen in the presence of adjuvant could be an attractive needle-free and self-administered immunotherapy for allergic diseases.

Background Ulcerative colitis (UC) is a chronic inflammatory autoimmune disease with limited treatment modalities. The animal model of colitis induced by treatment with trinitrobenzene sulfonic acid (TNBS-colitis) is commonly used to test new therapies of this disease. In our previous work we found that epicutaneous (EC) immunization with protein antigen induced a state of profound immunosuppression that inhibited inflammatory response in contact sensitivity, in experimental autoimmune encephalomyelitis (EAE) and in allogeneic skin graft rejection. Methods TNBS-induced colitis was used as an experimental model. Results In our current work, we showed that EC immunization with TNP-conjugated mouse immunoglobulin (TNP-Ig) prior to induction of TNBS-colitis alleviates disease severity what was determined by the body weight, the length and the weight of the colon, the histological activity index (HAI) and myeloperoxidase activity (MPO). Observed amelioration of the disease in TNP-Ig patched mice was accompanied with decreased production of IFN-γ and IL-17A by splenocytes. Additionally, spleen cells isolated from mice EC immunized with TNP-Ig prior to colitis induction showed increased production of IL-10 suggesting that this cytokine might be involved in inhibiting inflammatory response in the colon. Conclusion This work shows that EC immunization with protein antigen prior to TNBS-colitis induction ameliorates disease and observed suppression of inflammatory response in the colon might be mediated by IL-10.

Natural killer T cells with invariant αβ-T cell receptors (TCRs) (iNKT cells) constitute a lipid-responsive arm of the innate immune system that has been implicated in the regulation or promotion of various immune, infectious and neoplastic processes. Contact sensitivity (CS), also known as contact hypersensitivity or allergic contact dermatitis, is one such immune process that begins with topical sensitization to an allergen and culminates in a localized cutaneous inflammatory response after challenge with the same allergen. CS depends on events initiated early in sensitization by hepatic iNKT cells. We have shown previously that these iNKT cells release IL-4 early after skin sensitization to activate B-1 B cells to produce IgM antibodies that aid in local recruitment of the effector T cells. Here, we utilize adoptive transfer techniques in several strains of knockout mice to demonstrate that hepatic lipids isolated 30 min after sensitization are significantly more stimulatory to naive hepatic iNKT cells than hepatic lipids isolated after sham sensitization. These stimulatory hepatic lipids specifically affect iNKT cells and not B-1 B cells. The downstream CS response is abrogated with anti-CD1d-blocking antibodies, suggesting a critical role of CD1d in the activation of hepatic iNKT cells with these lipids. Hepatocytes may not be essential, as donor hepatic iNKT cells can reconstitute CS without migrating to the recipient mouse liver. Rather, CD1d-expressing liver mononuclear cells are sufficient for activation of iNKT cells. In conclusion, stimulatory lipids accumulate in the liver soon after sensitization and facilitate iNKT cell activation in a CD1d-dependent yet potentially hepatocyte-independent manner.

Prior studies of classical 24 h responses in TNP-Cl (picryl chloride) allergic contact sensitivity (CS), showed mediation by Th1 cells in CBA mice, and established that 24 h elicitation of responses requires an early 2 h CS-initiating component dependent on iNKT cells, IL-4 and B-1 B cells. Here, we studied the other form of cytotoxic T cell (Tc1) CS in DNFB sensitized BALB/c mice and determined that similar CS-initiation also is required. We systematically tested each step of the initiation pathway in this model. Thus, DNFB Tc1 CS was significantly impaired in iNKT cell deficient CD1d(-/-) and Jα18(-/-) mice, IL4Rα(-/-) and STAT-6(-/-) mice, and also in pan B-cell deficient JH(-/-) mice. Further, the Tc1 DNFB CS-initiating component, like Th1 response to TNP-Cl, was elicited by only 1-day after immunization, due to B-1 cells. In summary, we show that CS-Initiation also is required in Tc1 CS. Further, we have newly determined regulatory support of both the early and late components of DNFB induced Tc1 CS by iNKT cells and γδ-T cells. In summary, both iNKT cells and assisting γδ-T cells are involved in initiating and effector phases of DNFB induced CS.

Background: We have shown previously, in an animal model of multiple sclerosis and in TNBS-induced colitis, that epicutaneous (EC) immunization with protein antigen induces T suppressor cells that strongly inhibit the inflammatory response in contact hypersensitivity reactions. Methods: EC immunization was performed by applying to the shaved skin of the mouse dorsum a gauze patch soaked with a solution containing various amounts of type II collagen (COLL II) in a volume of 100 µl of PBS on days 0 and 4. On day 7 the patches were removed and mice were intradermally (i.d.) immunized with COLL II to induce collagen-induced arthritis (CIA). Results: Our study shows that EC immunization with 100 or 30 μg of COLL II reduces disease severity, whereas lower doses (10 or 3 μg) do not affect CIA. Decreased disease severity observed after EC immunization with COLL II correlates with reduced myeloperoxidase activity in joint tissue and with reduced production of anti-citrullinated protein and anti-COLL II IgG2a antibodies. Transfer experiments show that EC immunization with COLL II induces suppressor cells that belong to the population of TCRαβ lymphocytes and that EC-induced suppression declines with time. Both in vitro and in vivo experiments show that IL-17A plays an important role in EC-induced suppression of CIA. EC application of COLL II at the first signs of CIA also results in disease suppression. Conclusions: The suppression of inflammatory responses by T suppressor cells induced through EC immunization of a protein antigen may become an attractive noninvasive therapeutic method for a variety of clinical situations.

Background Epicutaneous (EC) immunization is a potential new strategy of a needle-free and self-administrable immunization by using a topically applied patch to deliver vaccine. We have previously shown that EC immunization with various protein antigens inhibits both Th1- and Tc1-mediated contact hypersensitivity (CHS) in mice. Our further work showed that maneuver of EC immunization with an antigen and Toll-like receptor (TLR) ligands prior to hapten sensitization reverses skin-induced suppression. Methods Animal model of pneumococcal pneumonia was used to study efficacy of EC induced immunopotentiation. Results Current work showed that EC immunization with phosphorylcholine conjugated to bovine serum albumin (PC-BSA) and CpG prior to Streptococcus pneumoniae infection results in smaller decrease of body weight when compared to PBS treated mice. Consistent with the behavioral observations and body weight, smaller numbers of bacteria were quantitated in lung homogenates of mice patched with PC-BSA and CpG prior inoculation with S. pneumonia when compared to mice patched with PBS alone. In vitro experiments showed that lymph node cells and spleen cells from mice EC immunized with PC-BSA plus CpG produced high levels of IFN-γ and IL-17A when compared to PBS or PC-BSA or CpG treated mice. Conclusion This work shows that EC immunization with PC-BSA plus TLR9 ligand CpG may be a potential tool to boost immunity to S. pneumoniae .

Background: Our previous work showed that epicutaneous (EC) immunization with protein antigen e.g. TNP-conjugated mouse immunoglobulin (TNP-Ig) in the form of a patch prior to hapten sensitization inhibits Th1-mediated contact hypersensitivity (CHS) in mice. We also found that suppression of CHS was mediated by TCRαβ+ CD4+ CD8+ T suppressor cells producing TGF-β. The aim of this study was to investigate the role of innate immunity in the suppression of CHS. Methods: Mice were immunized by applying gauze patches containing protein antigen alone or in the presence of zymosan, and were then tested for the CHS response. Adoptive cell transfer experiments were used to study the mechanisms involved in the reversal of skin-induced suppression. The influence of EC immunization on cytokine production by lymph node cells was measured by ELISA. Results: We found that EC immunization with TNP-Ig and zymosan before trinitrophenyl chloride sensitization reverses skin-induced suppression, demonstrated in vivo and in vitro. The reversal of skin-induced suppression was transferable by antigen-specific TCRαβ+ CD4+ T contrasuppressor cells. Furthermore, we showed that the contrasuppression was IL-17A-dependent and TLR2- and MyD88-independent. Conclusions: Our work strongly suggests that EC immunization with protein antigen and zymosan reverses skin-induced suppression and that this approach may be a potential tool to increase the immunogenicity of weakly immunogenic antigens.

Background Epicutaneous (EC) immunization offers a new method of a needle-free and self-administrable immunization by using a topically applied patch to deliver vaccine. We have previously shown that EC immunization with hapten-conjugated protein antigen TNP-Ig prior to hapten sensitization inhibits Th1-mediated contact hypersensitivity (CHS) in mice. Our further work showed that EC immunization with TNP-Ig and Toll-like receptor (TLR) ligands prior to hapten sensitization reverses skin-induced suppression. Methods Animal model of contact hypersensitivity was used to study reversal of skin-induced suppression. Results Current work showed that EC immunization with protein antigen TNP-Ig and MDP NOD2 agonist – muramyldipeptide (L isoform) reverses skin-induced suppression of CHS. On the other hand L18-MDP NOD2 agonist – muramyldipeptide with a C18 fatty acid chain and MDP control – negative control for MDP – muramyldipeptide (D isoform, inactive) did not reverse skin-induced suppression. “Transfer in” experiment showed that reversal of skin-induced suppression can be adoptively transferred with lymphoid cells isolated from donors EC treated with TNP-Ig and MDP NOD2 agonist. Moreover, experiment employing two non-cross-reacting antigens TNP-Ig and OX-Ig proved that reversal of skin-induced suppression is antigen specific. Additionally, lymph node cells isolated from mice EC immunized with TNP-Ig and MDP NOD2 agonist produced increased level of IFN-γ suggesting that this cytokine might be involved in reversal of skin-induced suppression. Conclusion This work shows that EC immunization with protein antigen plus NOD2 ligand MDP may be a potential tool to increase the immunogenicity of weekly immunogenic antigens.

Contact hypersensitivity (CHS) is an experimental model of allergic contact dermatitis (ACD) that can be studied in mice. For CHS responses, mice are immunized by painting with a reactive hapten, such as 1-fluoro-4,6-dinitrobenzene (DNFB), on the shaved abdominal and chest skin. Subsequently, the ears are challenged with diluted hapten, eliciting 'hypersensitive' ear-swelling reactions, which can be measured with a micrometer. In this manuscript we present complementary methods that can be used to evaluate CHS in mice that include: ear weight, vascular permeability, myeloperoxidase (MPO) activity, IFN-γ concentration in ear extracts and also IFN-γ production by auricular lymph node cells (ELNC). The biochemical evaluation of CHS can be also supported by proliferation assay, measurement of IFN-γ production by skin-draining lymph node cells employing ELISA test and by evaluation of IFN-γ(+) TCRαβ CD8 cells with the use of flow cytometry.

Background Allergic contact dermatitis (ACD) resulting from exposure to low molecular weight chemicals is a common clinical condition in industrialized countries and can be mediated by either Th1 or Tc1 lymphocytes. The animal model of contact sensitivity (CS) is commonly used to study ACD in mice and helps to test new therapeutics. We have previously shown that epicutaneous (EC) immunization with TNP-Ig prior to hapten sensitization inhibits Th1 -mediated CS and observed that the suppression is mediated by TCRαβ + CD4 + CD8 + cells and is TGF-β dependent. More recently we have shown that EC immunization with DNP-BSA induces TCRαβ + CD4 + CD25 + FoxP3 + T regulatory (Treg) cells that suppress Tc1-mediated CS. Methods Animal model of contact sensitivity was used to study skin-induced suppression. Results Current work employing Tc1-mediated CS shows that skin-induced suppression is dose-dependent and declines with time. Experiments with the four non-cross-reacting antigens 2,4-dinitrophenylated bovine serum albumin (DNP-BSA), ovalbumin (OVA), myelin basic protein (MBP) and immunoglobulins conjugated with oxazolone (OX-Ig) employing models of active suppression, “transfer in” and “transfer out” protocols showed that EC immunization with any tested protein antigen inhibits CS response suggesting lack of antigen-specificity of the investigated phenomenon. Conclusions The ease of EC generation of antigen-non-specific regulatory cells may have important implications for designing therapeutic schemes aimed at modulating immune responses.

As we have shown previously that protein antigen applied epicutaneously (EC) in mice inhibits TNP-specific Th1-mediated contact sensitivity (CS), we postulated that the maneuver of EC immunization might also suppress Tc1-dependent CS response. Here we showed that EC immunization of normal mice with 2,4-dinitrophenylated bovine serum albumin (DNP-BSA) applied on the skin in the form of a patch induces a state of subsequent unresponsiveness due to regulatory T cells (Treg) that inhibited sensitization and elicitation of effector T-cell responses. Suppression is transferable in vivo by TCRαβ(+) CD4(+) CD25(+) lymphocytes harvested from lymph nodes (LNs) of skin-patched animals. Flow cytometry revealed that EC immunization with DNP-BSA increased TCRαβ(+) CD4(+) CD25(+) FoxP3(+) lymphocytes in subcutaneous LNs, suggesting that observed suppression was mediated by Treg cells. Further, in vitro experiments showed that EC immunization with DNP-BSA prior to 1-fluoro-2,4-dinitrobenzen sensitization suppressed LN cell proliferation and inhibited production of TNF-α, IL-12 and IFN-γ. Using a transwell system or anti-CTLA-4 mAb, we found that EC induced suppression required direct Treg-effector cell contact and is CTLA-4-dependent.