krn-7000 and Chlamydia-Infections

The role of invariant NKT (iNKT) cells in reactive arthritis is unknown. We explored the functional role of NKT cells in reactive arthritis using an established murine model of Chlamydia trachomatis-induced arthritis (CtIA). CtIA in wild-type and CD1d knockout (KO) mice was induced by intra-articular injection of C. trachomatis. The effect of alpha-galactosylceramide (alpha-GalCer) activation of iNKT cells was investigated by intra-peritoneal administration of alpha-GalCer. Histopathological and phenotypic changes, chlamydial clearance and cytokine and chemokine production in synovial tissue of the knee joint were investigated after onset of the arthritis. The severity of CtIA was significantly increased in CD1d KO mice, which was associated with decrease in bactericidal cytokine IFN-gamma, regulatory cytokines IL-4 and IL-10 and increase in pro-inflammatory chemokines macrophage inflammatory protein-2 (MIP-2) and IFN-gamma-inducible protein-10 (IP-10). Local clearance of the pathogen from the joint was also decreased. Prior treatment of mice with alpha-GalCer, a potent activator of iNKT cells, significantly reduced the severity of CtIA in mice. The amelioration of CtIA was associated with decrease in chlamydial load and induction of cytokines IFN-gamma, IL-4 and IL-10 and significant suppression of MIP-2 and IP-10. Treatment of established CtIA with alpha-GalCer also demonstrated modulation of CtIA and decrease in chlamydial load. These results suggest that iNKT cells are protective against CtIA and alpha-GalCer-activated iNKT cells have an immunoregulatory role not only in preventing the induction of reactive arthritis but also in modulating established disease.

Topics: Animals; Antigens, CD1d; Arthritis, Experimental; Arthritis, Infectious; Chemokine CXCL10; Chemokine CXCL2; Chlamydia Infections; Chlamydia trachomatis; Galactosylceramides; Interferon-gamma; Interleukin-10; Interleukin-4; Lymphocyte Activation; Male; Mice; Mice, Inbred BALB C; Mice, Knockout; Natural Killer T-Cells; Tumor Necrosis Factor-alpha

We used two approaches to examine the role of NK T cells (NKT) in an intracellular bacterial (Chlamydia trachomatis mouse pneumonitis (C. muridarum)) infection. One is to use CD1 gene knockout (KO) mice, which lack NKT, and the other is to activate NKT using alpha-galactosylceramide (alpha-GalCer), a natural ligand of these cells. The data showed a promoting effect of NKT activation on Chlamydia lung infection. Specifically, CD1 KO mice exhibited significantly lower levels of body weight loss, less severe pathological change and lower chlamydial in vivo growth than wild-type mice. Immunological analysis showed that CD1 KO mice exhibited significantly lower C. muridarum-specific IL-4 and serum IgE Ab responses as well as more pronounced delayed-type hypersensitivity response compared with wild-type controls. In line with the finding in KO mice, the in vivo stimulation of NKT using alpha-GalCer enhanced chlamydial growth in vivo, which were correlated with reduced delayed-type hypersensitivity response and increased C. muridarum-driven IL-4/IgE production. Moreover, neutralization of IL-4 activity in the alpha-GalCer-treated BALB/c mice significantly reduced the promoting effect of alpha-GalCer treatment on chlamydial growth in vivo. These data provide in vivo evidence for the involvement of NKT in a bacterial pathogenesis and its role in promoting Th2 responses during infection.

Topics: Animals; Antigens, CD1; Chlamydia Infections; Chlamydia muridarum; Cytokines; Galactosylceramides; Hypersensitivity, Delayed; Immunoglobulin E; Immunoglobulin G; Killer Cells, Natural; Lung; Lymphocyte Activation; Mice; Mice, Inbred BALB C; Mice, Knockout; Pneumonia, Bacterial; Th2 Cells