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Aims: Sphingosine-1-phosphate receptor (S1PR) modulating therapies are currently in the clinic or undergoing investigation for multiple sclerosis (MS) treatment. However, the expression of S1PRs is still unclear in the central nervous system under normal conditions and during neuroinflammation., Methods: Using immunohistochemistry we examined tissues from both grey and white matter MS lesions for sphingosine-1-phosphate receptor 1 (S1P1 ) and 5 (S1P5 ) expression. Tissues from Alzheimer's disease (AD) cases were also examined., Results: S1P1 expression was restricted to astrocytes and endothelial cells in control tissues and a decrease in endothelial cell expression was found in white matter MS lesions. In grey matter MS lesions, astrocyte expression was lost in active lesions, while in quiescent lesions it was restored to normal expression levels. CNPase colocalization studies demonstrated S1P5 expression on myelin and both were reduced in demyelinated lesions. In AD tissues we found no difference in S1P1 expression., Conclusion: These data demonstrate a differential modulation of S1PRs in MS lesions, which may have an impact on S1PR-directed therapies., (© 2013 British Neuropathological Society.)

Lymphocyte trafficking is critically regulated by the Sphingosine 1-phosphate receptor-1 (S1P(1)), a G protein-coupled receptor that has been highlighted as a promising therapeutic target in autoimmunity. Fingolimod (FTY720, Gilenya) is a S1P(1) receptor agonist that has recently been approved for the treatment of multiple sclerosis (MS). Here, we report the discovery of NIBR-0213, a potent and selective S1P(1) antagonist that induces long-lasting reduction of peripheral blood lymphocyte counts after oral dosing. NIBR-0213 showed comparable therapeutic efficacy to fingolimod in experimental autoimmune encephalomyelitis (EAE), a model of human MS. These data provide convincing evidence that S1P(1) antagonists are effective in EAE. In addition, the profile of NIBR-0213 makes it an attractive candidate to further study the consequences of S1P(1) receptor antagonism and to differentiate the effects from those of S1P(1) agonists., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

FTY720 (fingolimod) has demonstrated efficacy in multiple sclerosis (MS). We evaluated the effects of FTY720 on progressive disability, viral load, and antibody responses in mice infected with Theiler's murine encephalomyocarditis virus (TMEV). FTY720 and phosphorylated FTY720 (FTY720-P) were detected in the brain after intraperitoneal injection of the drug. Bioactivity of FTY720 was confirmed by reduced numbers of mononuclear cells in the spleen and blood after treatment. No significant differences were found in disability progression, viral load, and serum antibody responses between the FTY720-treated versus the PBS-treated mice. There was less production of IgG within the CNS in the FTY-treated group on some measures., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: Angiogenesis is a common finding in chronic inflammatory diseases; however, its role in multiple sclerosis (MS) is unclear. Central nervous system lesions from both MS and experimental autoimmune encephalomyelitis (EAE), the animal model of MS, contain T cells, macrophages and activated glia, which can produce pro-angiogenic factors. Previous EAE studies have demonstrated an increase in blood vessels, but differences between the different phases of disease have not been reported. Therefore we examined angiogenic promoting factors in MS and EAE lesions to determine if there were changes in blood vessel density at different stages of EAE., Methods: In this series of experiments we used a combination of vascular casting, VEGF ELISA and immunohistochemistry to examine angiogenesis in experimental autoimmune encephalomyelitis (EAE). Using immunohistochemistry we also examined chronic active MS lesions for angiogenic factors., Results: Vascular casting and histological examination of the spinal cord and brain of rats with EAE demonstrated that the density of patent blood vessels increased in the lumbar spinal cord during the relapse phase of the disease (p < 0.05). We found an increased expression of VEGF by inflammatory cells and a decrease in the recently described angiogenesis inhibitor meteorin. Examination of chronic active human MS tissues demonstrated glial expression of VEGF and glial and blood vessel expression of the pro-angiogenic receptor VEGFR2. There was a decreased expression of VEGFR1 in the lesions compared to normal white matter., Conclusions: These findings reveal that angiogenesis is intimately involved in the progression of EAE and may have a role in MS.

Complement factor C3 is the central component of the complement system and a key inflammatory protein activated in Alzheimer's disease (AD). Previous studies demonstrated that inhibition of C3 by overexpression of soluble complement receptor-related protein y in an AD mouse model led to reduced microgliosis, increased amyloid beta (Abeta) plaque burden, and neurodegeneration. To further address the role of C3 in AD pathology, we generated a complement C3-deficient amyloid precursor protein (APP) transgenic AD mouse model (APP;C3(-/-)). Brains were analyzed at 8, 12, and 17 months of age by immunohistochemical and biochemical methods and compared with age-matched APP transgenic mice. At younger ages (8-12 months), no significant neuropathological differences were observed between the two transgenic lines. In contrast, at 17 months of age, APP;C3(-/-) mice showed significant changes of up to twofold increased total Abeta and fibrillar amyloid plaque burden in midfrontal cortex and hippocampus, which correlated with (1) significantly increased Tris-buffered saline (TBS)-insoluble Abeta(42) levels and reduced TBS-soluble Abeta(42) and Abeta(40) levels in brain homogenates, (2) a trend for increased Abeta levels in the plasma, (3) a significant loss of neuronal-specific nuclear protein-positive neurons in the hippocampus, and (4) differential activation of microglia toward a more alternative phenotype (e.g., significantly increased CD45-positive microglia, increased brain levels of interleukins 4 and 10, and reduced levels of CD68, F4/80, inducible nitric oxide synthase, and tumor necrosis factor). Our results suggest a beneficial role for complement C3 in plaque clearance and neuronal health as well as in modulation of the microglia phenotype.

Background: Activation of microglia is a part of the inflammatory response in neurodegenerative diseases but its role in the pathophysiology of these diseases is still unclear. The osteopetrotic (op/op) mouse lacks colony-stimulating factor-1 (CSF-1) and thus has a deficiency in microglia and macrophages. Prior reports have demonstrated that op/op mice deposit amyloid beta (Abeta) plaques, similar to those found in Alzheimer's disease. The purpose of these studies was to confirm this and to determine if the lack of CSF-1 affects the development of dopaminergic neurons and the expression of CD200, a known microglial inhibitory protein., Method: We examined the central nervous system of op/op mice at 30 days, 60 days and 7 months of age and wildtype littermates at 30 days using immunohistochemistry and histochemistry., Results: We found a decrease in the number of microglia in 1 month-old op/op mice compared to wildtype (WT) littermates as measured by CD11b, CD45, CD32/16, CD68, CD204 and F4/80 immunoreactivity. Abeta plaques were not detected, while the number of dopaminergic neurons appeared normal. The expression of CD200 appeared to be normal, but there appeared to be a lower expression in the substantia nigra., Conclusion: In contrast to a prior report we did not detect Abeta deposition in the central nervous system of op/op mice at 30 days, 60 days or 7 months of age and there was a normal number of dopaminergic neurons. This indicates that op/op mice may be useful to examine the effects of microglia on neurodegenerative disease progression by breeding them to different transgenic mouse models. In addition, the lack of CSF-1 does not appear to affect CD200 expression by neurons but we did note a decrease in the substantia nigra of op/op and WT mice, suggesting that this may be a mechanism by which microglia control may be attenuated in this specific area during Parkinson's disease.

Active and passive Abeta immunotherapy in Alzheimer's disease (AD)-like mouse models lowers cerebral amyloid-beta protein (Abeta) levels, especially if given early in the disease process, and improves cognitive deficits. In 2002, a Phase IIa clinical trial was halted due to meningoencephalitis in approximately 6% of the AD patients. It is hypothesized that the immunogen, full-length Abeta1-42, may have led to an autoimmune response. Currently, we are developing novel Abeta peptide immunogens for active immunization in amyloid precursor protein transgenic mice (APP Tg) to target Abeta B cell epitopes (within Abeta1-15) and avoid Abeta-specific T cell epitopes (Abeta16-42) so as to generate a safe and effective AD vaccine. Intranasal immunization with dendrimeric Abeta1-15 (16 copies of Abeta1-15 on a lysine core) or a tandem repeat of Abeta1-15 joined by 2 lysines and conjugated to an RGD motif with a mutated form of an E. coli-derived adjuvant generated robust Abeta titers in both wildtype and APP Tg mice. The Abeta antibodies recognized a B cell epitope within Abeta1-7, were mostly T-helper 2 associated immunoglobulin isotypes, bound human AD and APP Tg plaques, and detected Abeta oligomers. Splenic T cells reacted to the immunogens but not full-length Abeta. Six months of intranasal immunization (from 6-to-12 months of age) of J20 mice with each immunogen lowered insoluble Abeta42 by 50%, reduced plaque burden and gliosis, and increased Abeta in plasma. Interestingly, Abeta antibody generation was influenced by route of immunization. Transcutaneous immunization with dbeta1-15, but not full-length Abeta, led to high Abeta titers. In summary, our short Abeta immunogens induced robust titers of predominantly Th2 antibodies that were able to clear cerebral Abeta in the absence of Abeta-specific T cell reactivity, indicating the potential for a safer vaccine. We remain optimistic about the potential of such a vaccine for prevention and treatment of AD.

Immunization of humans and APP-tg mice with full-length beta-amyloid (Abeta) results in reduced cerebral Abeta levels. However, due to adverse events in the AN1792 trial, alternative vaccines are required. We investigated dendrimeric Abeta1-15 (dAbeta1-15), which is composed of 16 copies of Abeta1-15 peptide on a branched lysine core and thus, includes an Abeta-specific B cell epitope but lacks the reported T cell epitope. Immunization by subcutaneous, transcutaneous, and intranasal routes of B6D2F1 wildtype mice led to anti-Abeta antibody production. Antibody isotypes were mainly IgG1 for subcutaneous or transcutaneous immunization and IgG2b for intranasal immunization, suggestive of a Th2-biased response. All Abeta antibodies preferentially recognized an epitope in Abeta1-7. Intranasal immunization of J20 APP-tg mice resulted in a robust humoral immune response with a corresponding significant reduction in cerebral plaque burden. Splenocyte proliferation against Abeta peptide was minimal indicating the lack of an Abeta-specific cellular immune response. Anti-Abeta antibodies bound monomeric, oligomeric, and fibrillar Abeta. Our data suggest that dAbeta1-15 may be an effective and potentially safer immunogen for Alzheimer's disease (AD) vaccination.

Background: Immunotherapy for Alzheimer's disease (AD) is emerging as a potential treatment. However, a clinical trial (AN1792) was halted after adverse effects occurred in a small subset of subjects, which may have been caused by a T cell-mediated immunological response. In general, aging limits the humoral immune response, therefore, immunogens and vaccination regimes are required that induce a strong antibody response with less potential for an adverse immune response., Method: In the current study, we immunized both wildtype and J20 APP-tg mice with a priming injection of Abeta1-40/42, followed by multiple intranasal boosts with the novel immunogen dAbeta1-15 (16 copies of Abeta1-15 on a lysine tree), Abeta1-15 peptide or Abeta1-40/42 full length peptide., Results: J20 APP-tg mice primed with Abeta1-40/42 subcutaneously and subsequently boosted intranasally with Abeta1-15 peptide did not generate a cellular or humoral immune response. In contrast, J20 APP-tg mice boosted intranasally with dAbeta1-15 or full length Abeta1-40/42 produced high levels of anti-Abeta antibodies. Splenocyte proliferation was minimal in mice immunized with dAbeta1-15. Wildtype littermates of the J20 APP-tg mice produced higher amounts of anti-Abeta antibodies compared to APP-tg mice but also had low T cell proliferation. The anti-Abeta antibodies were mainly composed of IgG2b and directed to an epitope within the Abeta1-7 region, regardless of the immunogen. Examination of the brain showed a significant reduction in Abeta plaque burden in the J20 APP-tg mice producing antibodies compared to controls. Biochemically, Abeta40 or Abeta42 were also reduced in brain homogenates and elevated in plasma but the changes did not reach significance., Conclusion: Our results demonstrate that priming with full length Abeta40/42 followed by boosting with dAbeta1-15 but not Abeta1-15 peptide led to a robust humoral immune response with a minimal T cell response in J20 APP-tg mice. In addition, Abeta plaque burden was reduced in mice producing anti-Abeta antibodies. Interestingly, wildtype mice produced higher levels of anti-Abeta antibodies, indicating that immune tolerance may be present in J20 APP-tg mice. Together, these data suggest that dAbeta1-15 but not Abeta1-15 peptide may be useful as a boosting immunogen in an AD vaccination regime.

Amyloid-beta (Abeta) immunotherapy lowers cerebral Abeta and improves cognition in mouse models of Alzheimer's disease (AD). A clinical trial using active immunization with Abeta1-42 was suspended after approximately 6% of patients developed meningoencephalitis, possibly because of a T-cell reaction against Abeta. Nevertheless, beneficial effects were reported in antibody responders. Consequently, alternatives are required for a safer vaccine. The Abeta1-15 sequence contains the antibody epitope(s) but lacks the T-cell reactive sites of full-length Abeta1-42. Therefore, we tested four alternative peptide immunogens encompassing either a tandem repeat of two lysine-linked Abeta1-15 sequences (2xAbeta1-15) or the Abeta1-15 sequence synthesized to a cross-species active T1 T-helper-cell epitope (T1-Abeta1-15) and each with the addition of a three-amino-acid RGD (Arg-Gly-Asp) motif (R-2xAbeta1-15; T1-R-Abeta1-15). High anti-Abeta antibody titers were observed in wild-type mice after intranasal immunization with R-2xAbeta1-15 or 2xAbeta1-15 plus mutant Escherichia coli heat-labile enterotoxin LT(R192G) adjuvant. Moderate antibody levels were induced after immunization with T1-R-Abeta1-15 or T1-Abeta1-15 plus LT(R192G). Restimulation of splenocytes with the corresponding immunogens resulted in moderate proliferative responses, whereas proliferation was absent after restimulation with full-length Abeta or Abeta1-15. Immunization of human amyloid precursor protein, familial AD (hAPP(FAD)) mice with R-2xAbeta1-15 or 2xAbeta1-15 resulted in high anti-Abeta titers of noninflammatory T-helper 2 isotypes (IgG1 and IgG2b), a lack of splenocyte proliferation against full-length Abeta, significantly reduced Abeta plaque load, and lower cerebral Abeta levels. In addition, 2xAbeta1-15-immunized hAPP(FAD) animals showed improved acquisition of memory compared with vehicle controls in a reference-memory Morris water-maze behavior test that approximately correlated with anti-Abeta titers. Thus, our novel immunogens show promise for future AD vaccines.

Activated microglia and reactive astrocytes invade and surround cerebral beta amyloid (Abeta) plaques in Alzheimer's disease (AD), but the role of microglia in plaque development is still unclear. In this study, minocycline was administered for 3 months, prior to and early in Abeta plaque formation in amyloid precursor protein transgenic mice (APP-tg). When minocycline was given to younger mice, there was a small but significant increase in Abeta deposition in the hippocampus, concurrent with improved cognitive performance relative to vehicle treated mice. If APP-tg mice received minocycline after Abeta deposition had begun, microglial activation was suppressed but this did not affect Abeta deposition or improve cognitive performance. In vitro studies demonstrated that minocycline suppressed microglial production of IL-1beta, IL-6, TNF, and NGF. Thus, minocycline has different effects on Abeta plaque deposition and microglia activation depending on the age of administration. Our data suggest that this may be due to the effects of minocycline on microglial function. Therefore, anti-inflammatory therapies to suppress microglial activation or function may reduce cytokine production but enhance Abeta plaque formation early in AD., (Copyright 2006 Wiley-Liss, Inc.)

Abeta vaccination or passive transfer of human-specific anti-Abeta antibodies are approaches under investigation to prevent and/or treat Alzheimer's disease (AD). Successful active Abeta vaccination requires a strong and safe adjuvant to induce anti-Abeta antibody formation. We compared the adjuvants monophosphoryl lipid A (MPL)/trehalose dicorynomycolate (TDM), cholera toxin B subunit (CTB) and Escherichia coli heat-labile enterotoxin LT(R192G) for their ability to induce a humoral and cellular immune reaction, using fibrillar Abeta1-40/42 as a common immunogen in wildtype B6D2F1 mice. Subcutaneous (s.c.) administration with MPL/TDM resulted in anti-Abeta antibodies levels up to four times higher compared to s.c. LT(R192G). Using MPL/TDM, the anti-Abeta antibodies induced were mainly IgG2b, IgG1 and lower levels of IgG2a and IgM, with a moderate splenocyte proliferation and IFN-gamma production in vitro upon stimulation with Abeta1-40/42. LT(R192G), previously shown by us to induce robust titers of anti-Abeta antibodies, generated predominantly IgG2b and IgG1 anti-Abeta antibodies with very low splenocyte proliferation and IFN-gamma production. Weekly intranasal (i.n.) administration over 11 weeks of Abeta40/42 with CTB induced only moderate levels of antibodies. All immunogens generated antibodies that recognized mainly the Abeta1-7 epitope and specifically detected amyloid plaques on AD brain sections. In conclusion, MPL/TDM, in addition to LT(R192G), is an effective adjuvant when combined with Abeta40/42 and may aid in the design of Abeta immunotherapy.

The local immune response is characterized by an increase in the rate of entry of lymphocytes from the blood into regional lymph nodes and changes in the output of cells in lymph. While significant data are available regarding the role of inflammation-induced vascular adhesion processes in regulating lymphocyte entry into inflamed tissues and lymph nodes, relatively little is known about the molecular processes governing lymphocyte exit into efferent lymph. We have defined a novel role for lymphatic endothelial cells in the regulation of lymphocyte exit during a delayed type hypersensitivity (DTH) response to mycobacterial purified protein derivative (PPD). Soluble, pro-adhesive factors were identified in efferent lymph concomitant with reduced lymphocyte output in lymph, which significantly increased lymphocyte binding to lymphatic endothelial cells. While all lymphocyte subsets were retained, CD4+ T cells appeared less susceptible than others. Among a panel of cytokines in inflammatory lymph plasma, interferon (IFN)-gamma alone appeared responsible for this retention. In vitro adhesion assays using physiological levels of IFN-gamma confirmed the interaction between recirculating lymphocytes and lymphatic endothelium. These data demonstrate a new level of immune regulation, whereby the exit of recirculating lymphocytes from lymph nodes is selectively and sequentially regulated by cytokines in a manner equally as complex as lymphocyte recruitment.

Active amyloid beta (A beta) vaccination has been shown to be effective in clearing cerebral A beta and improving cognitive function in mouse models of Alzheimer's disease. However, an A beta vaccine clinical trial was suspended after meningoencephalitis was detected in a subset of subjects. Passive immunization has been suggested to be a safer alternative to active A beta immunization but there are reports of increased risk of microhemorrhages associated with its administration in aged beta-amyloid precursor protein transgenic mice bearing abundant vascular amyloid deposition. In addition, the cost may be prohibitive for large-scale clinical use. Therefore, we are designing novel A beta immunogens that encompass the B cell epitope of A beta but lack the T cell-reactive sites. These immunogens induced the production of A beta-specific antibodies in the absence of an A beta-specific cellular immune response in wild-type mice and are being tested in beta-amyloid precursor protein transgenic mice. These data together with published reports from several other groups suggest that a safe, active A beta vaccine is a tenable goal., (Copyright 2005 S. Karger AG, Basel.)

Amyloid beta (A beta) immunization of amyloid precursor protein (APP)-transgenic (tg) mice with human A beta induces humoral immunity, however, the immune response to endogenous rodent A beta is unknown. Fourteen-month J20 APP-tg mice and non-tg littermates were immunized subcutaneously followed by chronic intranasal boosting with human or rodent A beta peptide and adjuvant LT(R192G). Rodent A beta-immunized APP-tg mice had anti-rodent A beta antibody levels of 257.8 micrograms/ml and those immunized with human A beta had anti-human A beta antibodies of 120.8 micrograms/ml. Non-tg littermates had anti-rodent and anti-human A beta antibody concentrations of 98.8 and 231.1 microgram/ml, respectively. Inter-species cross-reactivity was minimal. Anti-human A beta antibodies were predominately IgG1 and IgG2b, while anti-rodent A beta antibodies were equally IgG1, IgG2a, and IgG2b. Anti-human A beta antibodies recognized an epitope within human A beta1-9. Anti-rodent A beta antibodies did not stain Alzheimer's disease (AD) plaques but bound some plaques in APP-tg mice. Splenocytes proliferated modestly to their respective antigen and secreted low levels of IL-2 and IFN-gamma. Therefore, immunizing APP-tg and non-tg mice with rodent A beta resulted in a species-specific humoral response with modest T cell reactivity.

The cerebral accumulation of beta-amyloid (Abeta) is a pathological hallmark of Alzheimer's disease (AD). Abeta vaccination or anti-Abeta specific antibodies may be a possible therapeutic option for AD. Previously, we demonstrated variation in the humoral response between B6D2F1 and C57BL/6 during short term (14 weeks) Abeta immunization. In the present study, we determined the humoral and cellular immune responses in these same mouse strains to a longer period of Abeta vaccination and further refined the major B cell epitope to Ass1-7. B6D2F1 mice generated a greater humoral and Th1 immune response versus C57BL/6 mice. Immunization with 25 microg Abeta produced a greater T cell response in B6D2F1 mice compared to 50 or 100 microg Abeta but resulted in comparable humoral immunity. Thus, Abeta vaccination is affected by the genetic background and amount of Abeta peptide used as immunogen. These data may help explain some differences observed in Abeta immunization studies in mice of various genetic backgrounds and aid in the design of Abeta vaccines.

Amyloid beta (Abeta) protein immunotherapy lowers cerebral Abeta and improves cognition in mouse models of Alzheimer's disease (AD). Here we show that Caribbean vervet monkeys (Chlorocebus aethiops, SK) develop cerebral Abeta plaques with aging and that these deposits are associated with gliosis and neuritic dystrophy. Five aged vervets were immunized with Abeta peptide over 10 months. Plasma and cerebral spinal fluid (CSF) samples were collected periodically from the immunized vervets and five aged controls; one monkey per group expired during the study. By Day 42, immunized animals generated plasma Abeta antibodies that labeled Abeta plaques in human, AD transgenic mouse and vervet brains; bound Abeta1-7; and recognized monomeric and oligomeric Abeta but not full-length amyloid precursor protein nor its C-terminal fragments. Low anti-Abeta titers were detected in CSF. Abetax-40 levels were elevated approximately 2- to 5-fold in plasma and decreased up to 64% in CSF in immunized vervets. Insoluble Abetax-42 was decreased by 66% in brain homogenates of the four immunized animals compared to archival tissues from 13 age-matched control vervets. Abeta42-immunoreactive plaques were detected in frontal cortex in 11 of the 13 control animals, but not in six brain regions examined in each of the four immunized vervets. No T cell response or inflammation was observed. Our study is the first to demonstrate age-related Abeta deposition in the vervet monkey as well as the lowering of cerebral Abeta by Abeta vaccination in a non-human primate. The findings further support Abeta immunotherapy as a potential prevention and treatment of AD.

Alzheimer's disease is the most prevalent form of dementia worldwide. Therapies are desperately needed to prevent and cure the disease. Mouse models of amyloid-beta deposition [APP and PSAPP transgenic (tg) mice] have been useful in determining the role of amyloid-beta (A beta) in both the pathogenesis and cognitive changes in AD. In addition, they have allowed scientists to investigate potential AD therapies in living animals. Active and passive A beta immunizations have been employed successfully in APP and PSAPP tg mice to lower cerebral A beta levels and improve cognition. Optimization of immunization protocols and characterization of immune responses in wildtype mice have been reported. Based on the promising results of A beta immunization studies in mice, a clinical trial was initiated for A beta vaccination in humans with AD. Although no adverse effects were reported in the Phase I safety trials, about 5% of AD patients in the phase II clinical trial developed meningoencephalitis, ending the trial prematurely in March 2002. Studies in AD mouse models and wildtype mice may help elucidate the mechanism for these unwanted side effects and will be useful for testing newer, safer vaccines for future use in human clinical trials.

The lymphatic system has a critical role in the return of fluids, proteins, and cells to the circulatory system. However, the effects of stress, including exercise, on this system have not been adequately studied. We investigated the effect of a physiological dose (1 mg) of epinephrine (Epi) on lymph flow, cell concentration, and lymphocyte subsets in efferent subcutaneous lymph in sheep. Blood leukocyte numbers, differential, lymphocyte subsets, and blood and lymph pools of lymphocytes were determined simultaneously. A significant acute increase in lymph flow was followed by a post-injection decrease in flow and cellular output. No changes in lymphocyte subsets or pools of lymphocytes were seen in either blood or lymph. The timing of elevated plasma and lymph concentrations of Epi and norepinephrine (NE) corresponded with the increased lymph flow. In conclusion, Epi injection caused no change in lymphocyte subset distribution, leukocyte concentration, or pools of lymphocytes. A decrease in lymph flow and cellularity was documented post-injection, indicating that lymphatic tissue has no role in the leukocytosis seen after Epi injection. Lymphocyte retention by lymph nodes, however, may contribute to post-injection lymphopenia.

It is well documented that there is communication between the cerebral spinal fluid (CSF) and cervical lymphatics. Recently, it has been demonstrated that tumor necrosis factor alpha (TNF-alpha) introduced into the CSF appears in the cervical lymph. However, the functional significance of this is less clear. Here we describe a protocol to quantitate the efflux of TNF-alpha from the CSF into cervical lymph. In addition, we describe a methodology to examine the effects of an intracerebroventricular (i.c.v.) infusion of TNF-alpha on lymph volume, cellularity and cell phenotype. While TNF-alpha was recovered in the cervical lymph following infusion of 125-I labeled TNF-alpha, the dosage of TNF-alpha used in this study had no effect on cervical lymph flow, cellularity or cell subsets. This protocol can be used to study the efflux of i.c.v. injected macromolecules and their effects on lymphocytes in cervical lymph and the regional lymph nodes.

Tumour necrosis factor (TNF)-alpha is important in several central nervous system (CNS) inflammatory diseases, however, its role in the recruitment of leukocytes into the cerebral spinal fluid (CSF) and CNS is incompletely understood. Therefore, we examined the effect of intracerebroventricular (icv) and parenchymal infusions of TNF-alpha on the type of leukocyte, the pool and subset of lymphocytes recruited into CSF and brain parenchyma. Parenchymal injections of 500 ng of recombinant human TNF-alpha did not induce inflammation, whereas an icv infusion of TNF-alpha caused CSF leuckocytosis and a perivascular infiltrate. Twenty-four hours after the icv infusion neutrophils predominated, with CD4+ T cells being the major lymphocyte subset in CSF. By 48 h lymphocytes were the dominant cell type with CD8+ cells surpassing CD4+ cells in both the CSF and the perivascular infiltrate. The labeled recirculating lymphocyte pool prevailed in normal CSF, but after the infusion of TNF-alpha, the blood pool of lymphocytes was preferentially recruited. These results have implications for the immune surveillance of the CNS.

The spleen plays a major role in immune surveillance, but the impact that splenectomy exerts on the immune competence of an individual is not fully resolved. Here we show that neonatal splenectomy in sheep does not abrogate the development of a large, nonrecirculating pool of lymphocytes and that it has no effect on the acquisition of a normal blood lymphocyte profile. Splenectomy did, however, result in a significant decrease in blood residency time of recirculating lymphocytes and in an enhanced accumulation of recirculating lymphocytes in lymph nodes. Furthermore, nonrecirculating peripheral blood lymphocytes were less likely to migrate to the lung, possibly because of saturation of the marginal pool by recirculating lymphocytes. Although splenectomy has little effect on the development or distribution of lymphocyte subsets in blood and lymph, it has marked effects on the rate of recirculation of lymphocytes, which may have significant implications for peripheral immune surveillance in patients who undergo splenectomy.

TNF-alpha is one of the most potent immunoregulatory molecules in vivo. In addition to important regulatory effects, it is also a potent inducer of extravascular lymphocyte infiltration. To examine the dynamic changes that are induced in local lymphocyte migration through regional lymph nodes following TNF-alpha injection, we used a protocol of direct lymphatic cannulation to quantitatively and qualitatively examine the traffic of lymphocytes through regional lymph nodes. We observed that local TNF-alpha injection reduced the output of lymphocytes from lymph nodes up to 90% within 6-10 h following stimulation. TNF-alpha also altered the specificity of migration of lymphocyte traffic through subcutaneous lymph nodes. In addition to the decreased output, phenotypic analysis demonstrated decreases in the concentration of gamma delta T cells by up to 30% following TNF-alpha injection. Histological examination showed that the gamma delta T cells were found in close association with VCAM-1-expressing cells in TNF-stimulated lymph nodes, at least some of which appeared to be lymphatic endothelium. These data indicate that TNF-alpha is capable of altering the number and specificity of lymphocytes recirculating through stimulated lymph nodes by selectively altering the entry of lymphocytes into the efferent lymphatics of inflamed lymph nodes in vivo.

We have investigated the migration of lymphocytes from blood into the central nervous system (CNS) under normal physiological conditions. Using sheep as our model, we simultaneously sampled blood, lymph and cerebral spinal fluid (CSF). Normal, nonactivated, recirculating lymphocytes can migrate into the CSF in similar concentrations as found in subcutaneous lymph and there is no difference in the temporal appearance between them. Lymphocytes infused into the CNS could be found in cervical lymph nodes. These data suggest that lymphocytes found in the CNS are part of the recirculating lymphocyte pool and do not require activation to enter the CSF.

In this study we examined the new cell dye CM-DiI for tracking the migration of lymphocytes from blood to lymph. This lipophilic marker intercalates in the plasma membrane like the PKH dyes and older DiI derivatives. The stability and intensity of staining achieved with these dyes is better than most other fluorochromes or radioisotopes, yet they are poorly soluble in aqueous solutions, which can make staining difficult, and they are not fixable in tissue sections. CM-DiI is reported to have increased water solubility and it can be fixed using traditional aldehyde fixatives, making it feasible to detect labeled cells in histological sections. To determine the suitability of CM-DiI as a lymphocyte marker, a labeling protocol was developed. We tested the ability of stained cells to recirculate in vivo. Following the intravenous injection of CM-DiI positive cells, their recovery in lymph over 40 h was comparable to that of cells labeled with other fluorochromes or radioisotopes. The kinetics of recirculation were also very similar, as labeled cells were detectable in lymph within 4 h of injection, and the peak percentage of labeled cells in lymph was generally observed between 20-30 h. We also confirmed that CM-DiI is retained in the lymphocyte membrane following routine paraffin processing. Thus CM-DiI does not appear to alter the process of lymphocyte recirculation, and it should be a useful marker for tracking these cells.