Modulation of MOG 37-50-specific CD8+ T cell activation and expansion by CD43

Transplantation elicits a clonally diverse CD8+ T cell response that is comprised of potent CD43+ effectors

CD8+ T cells mediate acute rejection of allografts, which threatens the long-term survival of transplanted organs. Using MHC class I tetramers, we find that allogeneic CD8+ T cells are present at an elevated naive precursor frequency relative to other epitopes, only modestly increase in number after grafting, and maintain high T cell receptor diversity throughout the immune response. While antigen-specific effector CD8+ T cells poorly express the canonical effector marker KLRG-1, expression of the activated glycoform of CD43 defines potent effectors after transplantation. Activated CD43+ effector T cells maintain high expression of the coreceptor induced T cell costimulator (ICOS) in the presence of CTLA-4 immunoglobulin (Ig), and dual CTLA-4 Ig/anti-ICOS treatment prolongs graft survival. These data demonstrate that graft-specific CD8+ T cells have a distinct response profile relative to anti-pathogen CD8+ T cells and that CD43 and ICOS are critical surface receptors that define potent effector CD8+ T cell populations that form after transplantation.

Experimental Autoimmune Encephalomyelitis Inhibited by Huangqi Guizhi Wuwu Decoction via Th2 Cytokine Enhancement

Background:

Huangqi Guizhi Wuwu decoction (HQGZWW) exhibits good effects when administered to treat multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Understanding the precise mechanism of this decoction is thus important. Based on the findings of our previous study, the aim of the present study was to understand the role of antigen-specific CD8+ T-cells on the pathogenesis of MS/EAE when HQGZWW is administered as treatment.

Methods:

Myelin oligodendrocyte glycoprotein (MOG) 35-55-induced mice were administered distilled water, prednisone, and high dose or low dose HQGZWW. After purified CD4+ and CD8+ T-cells were stimulated with the MOG35-55 peptide, proliferation and cytokine secretion assays were performed. To establish the adoptive transfer EAE model, naïve mice were injected with MOG35-55 - CD8+ or CD4+ T-cells.

Results:

Significant improvements in EAE score and pathology were observed in the high dose HQGZWW and prednisone groups. Compared to the low dose HQGZWW and distilled water groups, lower antigen-specific responses, lower levels of interferon-gamma, and higher levels of interleukin (IL)-4 and IL-10 from CD8+ and CD4+ T cells were observed in the high dose HQGZWW and prednisone groups. Finally, the EAE score was observed to be similar between the high dose HQGZWW group and prednisone group; however, this finding was not observed in the low dose HQGZWW group.

Conclusion:

Our findings suggest that high dose HQGZWW has similar effects on cell proliferation, cytokine secretion, and EAE score to prednisone, while low dose HQGZWW does not have such effect. The protective role of HQGZWW against EAE might thus depend on the Th2 cytokine secretion profile induced by either MOG35-55 specific CD8+ or CD4+ T-cells.

CD43-mediated IFN-γ production by CD8+ T cells promotes abdominal aortic aneurysm in mice

CD43 is a glycosylated surface protein abundantly expressed on lymphocytes. Its role in immune responses has been difficult to clearly establish, with evidence supporting both costimulatory and inhibitory functions. In addition, its contribution to disease pathogenesis remains elusive. Using a well-characterized murine model of elastase-induced abdominal aortic aneurysm (AAA) that recapitulates many key features of the human disease, we established that the presence of CD43 on T cells is required for AAA formation. Moreover, we found that IFN-γ-producing CD8(+) T cells, but not CD4(+) T cells, promote the development of aneurysm by enhancing cellular apoptosis and matrix metalloprotease activity. Reconstitution with IFN-γ-producing CD8(+) T cells or recombinant IFN-γ promotes the aneurysm phenotype in CD43(-/-) mice, whereas IFN-γ antagonism abrogates disease in wild-type animals. Furthermore, we showed that the presence of CD43 with an intact cytoplasmic domain capable of binding to ezrin-radixin-moesin cytoskeletal proteins is essential for optimal in vivo IFN-γ production by T cells and aneurysm formation. We have thus identified a robust physiologic role for CD43 in a relevant animal model and established an important in vivo function for CD43-dependent regulation of IFN-γ production. These results further suggest that IFN-γ antagonism or selective blockade of CD43(+)CD8(+) T cell activities merits further investigation for immunotherapy in AAA.

Pathogenic MOG-reactive CD8+ T cells require MOG-reactive CD4+ T cells for sustained CNS inflammation during chronic EAE

XIncreasing evidence supports a role for CD8+ T cells in multiple sclerosis. In an attempt to isolate the contribution of CD8+ T cells in a murine model of MS, we immunized mice with a dominant CD8 epitope MOG37-46, a truncated version of MOG35-55. The data presented here show mild disease induced with MOG37-46, characterized by lower clinical scores, a decrease in CNS infiltration and a decrease in microglial activation. CD8+ T cells reactive to MOG37-46 are pro-inflammatory and traffic to the CNS; however, the presence of CD4+ T cells elicits more severe disease and sustained inflammation of the CNS.

Cerebral gene expression of superantigen encephalitis in the lewis rat induced by staphylococcal enterotoxin a

Superantigens were suggested to play a role in the pathogenesis of different autoimmune diseases including multiple sclerosis (MS). Previously, it was demonstrated that local expression of the superantigen, staphylococcal enterotoxin A (SEA) in the brain of rats may lead to encephalitis which was amplified by using intravenous injection of concanavalin A (ConA)-activated splenocytes. In the present investigation, gene expression was studied in the rat brain 8 days after an injection of 50 mul of 1 mg/ml SEA or saline and 5 days after an intravenous injection of 1 x 10(7) ConA-activated spleen cells. Of 8800 genes investigated (Affymetrix, rat genome U34A), the expression of 106 genes was significantly and at least threefold increased with SEA, while the expression of 29 genes was decreased at least threefold. Increased gene expression was compatible with an intracerebral inflammatory response mediated by antigen-presenting cells and CD8+ T lymphocytes. Elevated chemokines comprised RANTES (CCL5), osteopontin, MCP-1 (CCL2) and CXCL10. Further, genes with increased expression were assigned to the extracellular matrix, microglia/macrophage cell elements, astrocytes (GFAP) and phagocytosis. There was considerable conformity between previously reported gene expression profiles for experimental autoimmune encephalomyelitis (EAE) or MS and the present findings. Our data are in line with the concept that T-cell superantigen locally expressed in the central nervous system induces an inflammatory response. Therefore, the study of gene expression profiles does not seem to allow clear conclusions with respect to the aetiology of central nervous system autoimmune diseases.

Immunosuppressive effect of silibinin in experimental autoimmune encephalomyelitis

Silibinin is the major pharmacologically active compound of silymarin, the Silybum marianum fruit extract. Hepatoprotective activities of silibinin/silymarin are well-known, and recent studies demonstrated their anti-inflammatory and anti-carcinogenic effects which are due to inhibition of the transcription factor NF-kappaB. Based on this knowledge, we hypothesized that silibinin could be effective in the treatment of multiple sclerosis (MS) and so we tested its immunosuppressive effect in experimental autoimmune encephalomyelitis (EAE), the MS animal model. The process of spinal cord demyelination and inflammation were observed and T cell migration was determined by FACS analysis. The results showed that silibinin significantly reduced the histological signs of demyelination and inflammation in EAE. Since cytokines play an important role in inflammatory disease, the proliferative response and cytokine production were examined in lymphocytes from spleens and lymph nodes. We demonstrated that silibinin Ag-nonspecifically down-regulated the secretion of pro-inflammatory Th1 cytokines and up-regulated the anti-inflammatory Th2 cytokines in vitro. Silibinin also dose-dependently inhibited the production of Th1 cytokines ex vivo. These results indicate that silibinin is both immunosuppressive and immunomodulatory.

Myelin oligodendrocyte glycoprotein peptide-induced experimental allergic encephalomyelitis and T cell responses are unaffected by immunoproteasome deficiency

The inoculation of MOG peptides into C57BL/6 mice induces CD4(+) and CD8(+) T cells, and recent work has shown that adoptive transfer of the latter population, after extensive in vitro stimulation, can cause EAE in naïve recipient mice. Herein, we have evaluated the incidence and severity of EAE, and the induction of CD4(+) and CD8(+) T cells, following MOG peptide inoculation of wt mice and of LMP-2KO mice that lack an intact immunoproteasome, a cytoplasmic organelle that is induced by chronic inflammation and that may be important for the presentation of MHC class I epitopes to CD8(+) T cells. We report that EAE, evaluated by both clinical and histological criteria, is similar in LMP-2KO mice and wildtype C57B/6 mice (wt) in response to immunization with MOG peptides MOG(35-55) and MOG(40-54), suggesting that the immunoproteasome does not play a key role in the development of demyelinating disease. Furthermore, and consistent with previous reports, peptide-specific CD8(+) T cells were barely detectable in the CNS of peptide-immunized mice, although peptide-specific CD4(+) T cells were abundant. Therefore, we used a new technique to look for autoreactive CD8(+) T cells in MOG peptide-immunized mice, and we report the identification of CD4(+) and CD8(+) T cells that, as late as 19 days after peptide injection, are actively producing IFNgamma in vivo, in response to in vivo antigen contact.

Central histamine H3 receptor signaling negatively regulates susceptibility to autoimmune inflammatory disease of the CNS

Histamine (HA), a biogenic amine with a broad spectrum of activities in both physiological and pathological settings, plays a key regulatory role in experimental allergic encephalomyelitis, the autoimmune model of multiple sclerosis. HA exerts its effect through four G protein-coupled receptors designated HA receptor H1, H2, H3, and H4. We report here that, compared with wild-type animals, mice with a disrupted HA H3 receptor (H3RKO), the expression of which is normally confined to cells of the nervous system, develop more severe disease and neuroinflammation. We show that this effect is associated with dysregulation of blood-brain barrier permeability and increased expression of MIP-2, IP-10, and CXCR3 by peripheral T cells. Our data suggest that pharmacological targeting of the H3R may be useful in preventing the development and formation of new lesions in multiple sclerosis, thereby significantly limiting the progression of the disease.