Cutting edge: V alpha 14-J alpha 281 NKT cells naturally regulate experimental autoimmune encephalomyelitis in nonobese diabetic mice

Although deficiencies in the NKT cell population have been observed in multiple sclerosis and mouse strains susceptible to experimental autoimmune encephalomyelitis (EAE), little is known about the function of these cells in CNS autoimmunity. In this work we report that TCR Valpha14-Jalpha281 transgenic nonobese diabetic mice, which are enriched in CD1d-restricted NKT cells, are protected from EAE. The protection is associated with a striking inhibition of Ag-specific IFN-gamma production in the spleen, implying modulation of the encephalitogenic Th1 response. This modulation is independent of IL-4 because IL-4-deficient Valpha14-Jalpha281 mice are still protected against EAE and independent of NKT cell-driven Th1 to Th2 deviation, because no increased autoantigen-specific Th2 response was observed in immunized Valpha14-Jalpha281 transgenic mice. Our findings indicate that enrichment and/or stimulation of CD1d-dependent NKT cells may be used as a novel strategy to treat CNS autoimmunity.     

Regulation of experimental autoimmune encephalomyelitis in the C57BL/6J mouse by NK1.1+, DX5+, alpha beta+ T cells

C57BL/6 (B6) mice with targeted mutations of immune function genes were used to investigate the mechanism of recovery from experimental autoimmune encephalomyelitis (EAE). The acute phase of passive EAE in the B6 mouse is normally resolved by partial recovery followed by mild sporadic relapses. B6 TCR beta-chain knockout (KO) recipients of a myelin oligodendrocyte glycoprotein p35-55 encephalitogenic T cell line failed to recover from the acute phase of passive EAE. In comparison with wild-type mice, active disease was more severe in beta(2)-microglobulin KO mice. Reconstitution of TCR beta-chain KO mice with wild-type spleen cells halted progression of disease and favored recovery. Spleen cells from T cell-deficient mice, IL-7R KO mice, or IFN-gamma KO mice were ineffective in this regard. Irradiation or treatment of wild-type spleen cell population with anti-NK1.1 mAb before transfer abrogated the protective effect. Removal of DX5(+) cells from wild-type spleen cells by anti-DX5 Ab-coated magnetic beads before reconstitution abrogated the suppressive properties of the spleen cells. TCR-deficient recipients of the enriched DX5(+) cell population recovered normally from passively induced acute disease. DX5(+) cells were sorted by FACS into DX5(+) alpha beta TCR(+) and DX5(+) alpha beta TCR(-) populations. Only recipients of the former recovered normally from clinical disease. These results indicate that recovery from acute EAE is an active process that requires NK1.1(+), DX5(+) alpha beta(+) TCR spleen cells and IFN-gamma.     

In vivo regulation of experimental autoimmune encephalomyelitis by NK cells: alteration of primary adaptive responses

Innate immune responses provide the host with its first line of defense against infections. Signals generated by subsets of lymphocytes, including NK cells, NKT cells, and APC during this early host response determine the nature of downstream adaptive immune responses. In the present study, we have examined the role of innate NK cells in an autoimmune model through the use of primary immunization with the myelin oligodendrocyte glycoprotein peptide to induce experimental autoimmune encephalomyelitis (EAE). Our studies have shown that in vivo depletion of NK cells can affect the adaptive immune responses, because NK cells were found to regulate the degree of clinical paralysis and to alter immune adaptive responses to the myelin oligodendrocyte glycoprotein peptide. The requirement for NK cells was reflected by changes in the T cell responses and diminished clinical disease seen in mice treated with anti-NK1.1, anti-asialo GM1, and selected Ly49 subtype-depleted mice. In addition to alteration in T cell responses, the maturational status of dendritic cells in lymph nodes was altered both quantitatively and qualitatively. Finally, examination of TCR Vbeta usage of the brain lymphocytes from EAE mice indicated a spectra-type change in receptor expression in NK- depleted mice as compared with non-NK-depleted EAE mice. These findings further establish a recently postulated link between NK cells and the generation of autoreactive T cells.     

Roles of TNF-related apoptosis-inducing ligand in experimental autoimmune encephalomyelitis

TRAIL, the TNF-related apoptosis-inducing ligand, induces apoptosis of tumor cells, but not normal cells; the roles of TRAIL in nontransformed tissues are unknown. Using a soluble TRAIL receptor, we examined the consequences of TRAIL blockade in an animal model of multiple sclerosis. We found that chronic TRAIL blockade in mice exacerbated experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein. The exacerbation was evidenced primarily by increases in disease score and degree of inflammation in the CNS. Interestingly, the degree of apoptosis of inflammatory cells in the CNS was not affected by TRAIL blockade, suggesting that TRAIL may not regulate apoptosis of inflammatory cells in experimental autoimmune encephalomyelitis. By contrast, myelin oligodendrocyte glycoprotein-specific Th1 and Th2 cell responses were significantly enhanced in animals treated with the soluble TRAIL receptor. Based on these observations, we conclude that unlike TNF, which promotes autoimmune inflammation, TRAIL inhibits autoimmune encephalomyelitis and prevents activation of autoreactive T cells.     

NKT cells in the rat: organ-specific distribution of NK T cells expressing distinct V alpha 14 chains

Rat invariant TCR alpha-chains and NKT cells were investigated to clarify whether CD1d-mediated recognition by NKT cells is conserved further in evolution. Rats had multiple-copies of TRAV14 genes, which can be categorized into two types according to the diversity accumulated in the CDR2 region. Rats retained invariant TCR alpha forms with the homogeneous junctional region similar to mouse invariant TRAV14-J281. The proportion of invariant TCR among V alpha 14+ clones was 12.9% in the thymus and increased in the periphery, 31% in the spleen and 95% in hepatic sinusoidal cells. The invariant TRAV14-J281 was expressed by liver sinusoidal and splenic NKT cells with CD8, CD44high, and TCR V beta 8. Type 1 invariant TCR alpha was expressed more frequently in hepatic lymphocytes, while type 2 invariant TCR alpha was expressed predominantly in the spleen. Both types of cells cytolyzed to and were stimulated to proliferate by CD1d-expressing cells in a CD1d-restricted manner. These results suggested that rat NKT cells bearing distinct V alpha 14 chains are distributed in a tissue-specific pattern. NKT cell populations in rats were more variable than those in mice, indicating that they play novel roles in nature. The implication of the molecular interaction between the structurally diverse invariant TCR alpha and CD1d/ligand complex in different organs is discussed.     

Delta-like ligand 4 regulates central nervous system T cell accumulation during experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a CD4(+) T cell-mediated inflammatory demyelinating disease of the CNS that serves as a model for multiple sclerosis. Notch receptor signaling in T lymphocytes has been shown to regulate thymic selection and peripheral differentiation. In the current study, we hypothesized that Notch ligand-receptor interaction affects EAE development by regulating encephalitogenic T cell trafficking. We demonstrate that CNS-infiltrating myeloid dendritic cells, macrophages, and resident microglia expressed Delta-like ligand 4 (DLL4) after EAE induction. Treatment of mice with a DLL4-specific blocking Ab significantly inhibited the development of clinical disease induced by active priming. Furthermore, the treatment resulted in decreased CNS accumulation of mononuclear cells in the CNS. Anti-DLL4 treatment did not significantly alter development of effector cytokine expression by Ag-specific T cells. In contrast, anti-DLL4 treatment reduced T cell mRNA and functional cell surface expression of the chemokine receptors CCR2 and CCR6. Adoptive transfer of Ag-specific T cells to mice treated with anti-DLL4 resulted in decreased clinical severity and diminished Ag-specific CD4(+) T cell accumulation in the CNS. These results suggest a role for DLL4 regulation of EAE pathogenesis through modulation of T cell chemokine receptor expression and migration to the CNS.     

IL-13 production by regulatory T cells protects against experimental autoimmune encephalomyelitis independently of autoantigen

Treatment with an anti-inflammatory Salmonella vaccine expressing enterotoxigenic Escherichia coli colonization factor Ag 1 (CFA/I) proved effective in stimulating protective, potent CD25(+)CD4(+) regulatory T (T(reg)) cells in susceptible mice challenged with experimental autoimmune encephalomyelitis (EAE). Because the Salmonella vector was considerably less protective, we questioned whether altering fimbrial subunit expression to resemble conventional Salmonella expression may impact T(reg) cell potency. The Salmonella-CFA/I vaccine was modified to limit fimbrial subunit expression to the intracellular compartment (Salmonella-CFA/I(IC)). SJL mice were challenged with proteolipid protein peptide 139-151 to induce EAE and orally treated with one of three Salmonella vaccines 6 days postchallenge. Treatment with Salmonella-CFA/I(IC) greatly reduced clinical disease, similarly as Salmonella-CFA/I, by subduing IL-17 and IL-21; however, mechanisms of protection differed as evident by increased IL-13 and IFN-gamma but diminished TGF-beta production by T(reg) cells from Salmonella-CFA/I(IC)-treated mice. Adoptive transfer of T(reg) cells from both CFA/I-expressing constructs was equivalent in protecting against EAE, showing minimal disease. Although not as potent in its protection, CD25(-)CD4(+) T cells from Salmonella-CFA/I(IC) showed minimal Th2 cells, but vaccination did prime these Th2 cells rendering partial protection against EAE challenge. In vivo IL-13 but not IFN-gamma neutralization compromised protection conferred by adoptive transfer with Salmonella-CFA/I(IC)-induced T(reg) cells. Thus, the Salmonella-CFA/I(IC) vaccine elicits T(reg) cells with attributes from both the Salmonella vector and Salmonella-CFA/I vaccines. Importantly, these T(reg) cells can be induced to high potency by simply vaccinating against irrelevant Ags, offering a novel approach to treat autoimmune diseases independently of the autoantigen.     

Peripheral T cells are the therapeutic targets of glucocorticoids in experimental autoimmune encephalomyelitis

High-dose glucocorticoid (GC) therapy is widely used to treat multiple sclerosis (MS), but the underlying mechanisms remain debatable. In this study, we investigated the impact of GC administration on experimental autoimmune encephalomyelitis using different GC receptor (GR)-deficient mutants. Heterozygous GR knockout mice were less sensitive to dexamethasone therapy, indicating that the expression level of the receptor determines therapeutic efficacy. Mice reconstituted with homozygous GR knockout fetal liver cells showed an earlier onset of the disease and were largely refractory to GC treatment, indicating that the GR in hematopoietic cells is essential for the beneficial effects of endogenous GCs and dexamethasone. Using cell-type specific GR-deficient mice, we could demonstrate that GCs mainly act on T cells, while modulation of macrophage function was largely dispensable in this context. The therapeutic effects were achieved through induction of apoptosis and down-regulation of cell adhesion molecules in peripheral T(H)17 and bystander T cells, while similar effects were not observed within the spinal cord. In addition, dexamethasone inhibited T cell migration into the CNS, confirming that peripheral but not CNS-residing T lymphocytes are the essential targets of GCs. Collectively, our findings reveal a highly selective mechanism of GC action in experimental autoimmune encephalomyelitis and presumably multiple sclerosis.     

Trichinella spiralis: modulation of experimental autoimmune encephalomyelitis in DA rats

Helminth infection has a potent systemic immunomodulatory effect on the host immune response, which also affects the development of autoimmune diseases. We investigated the dose-dependent influence of Trichinella spiralis infection on experimental autoimmune encephalomyelitis (EAE). Our model of concomitant T. spiralis infection and EAE demonstrates that established infection of Dark Agouti (DA) rats with the parasite causes amelioration of the clinical course of induced EAE in a dose-dependent way. Infection with T. spiralis L1 stage muscle larvae (TSL1) reduced the severity of the autoimmune disease as judged by lower maximal clinical score, cumulative index, duration of illness and degree of mononuclear cell infiltration in T. spiralis infected animals compared to control, EAE-induced group. This study provides a valuable model of worm infection to investigate helminth-induced regulatory mechanisms for optimal benefit to the host.