These data suggest that natalizumab treatment results in a prolonged decrease of lymphocytes in the CSF and are consistent with the hypothesis that natalizumab impairs immune surveillance of the central nervous system.

Abbreviations used: CNS, central nervous system; EAE, experimental autoimmune encephalomyelitis; MBP, myelin basic protein; MS, multiple sclerosis; NS, nonsense. The extent to which myelin-specific Th1 and Th17 cells contribute to the pathogenesis of experimental autoimmune encephalomyelitis (EAE) is controversial. Combinations of interleukin (IL)-1, IL-6, and IL-23 with transforming growth factor  were used to differentiate myelin-specific T cell receptor transgenic T cells into Th17 cells, none of which could induce EAE, whereas Th1 cells consistently transferred disease. However, IL-6 was found to promote the differentiation of encephalitogenic Th17 cells. Further analysis of myelinspecific T cells that were encephalitogenic in spontaneous EAE and actively induced EAE demonstrated that T-bet expression was critical for pathogenicity, regardless of cytokine expression by the encephalitogenic T cells. These data suggest that encephalitogenicity of myelin-specific T cells appears to be mediated by a pathway dependent on T-bet and not necessarily pathway-specific end products, such as interferon  and IL-17. T-bet is

IL-17-producing T cells (Th17) have recently been implicated in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model for the human disease multiple sclerosis. However, little is known about the transcription factors that regulate these cells. Although it is clear that the transcription factor T-bet plays an essential role in the differentiation of IFN-γ-producing CD4+ Th1 lymphocytes, the potential role of T-bet in the differentiation of Th17 cells is not completely understood. In this study, therapeutic administration of a small interfering RNA specific for T-bet significantly improved the clinical course of established EAE. The improved clinical course was associated with suppression of newly differentiated T cells that express IL-17 in the CNS as well as suppression of myelin basic protein-specific Th1 autoreactive T cells. Moreover, T-bet was found to directly regulate transcription of the IL-23R, and, in doing so, influenced the fate of Th17 cells, which depend on optimal IL-23 production for survival. We now show for the first time that suppression of T-bet ameliorates EAE by limiting the differentiation of autoreactive Th1 cells, as well as inhibiting pathogenic Th17 cells via regulation of IL-23R.

Background: Treatment with natalizumab, a monoclonal antibody against the adhesion molecule very late activation antigen 4, an ␣4␤ 1 integrin, was recently associated with the development of progressive multifocal leukoencephalopathy, a demyelinating disorder of the central nervous system caused by JC virus infection. Objective: To test the effect of natalizumab treatment on the CD4 ϩ /CD8 ϩ T-cell ratios in cerebrospinal fluid (CSF) and peripheral blood.

SLE is a chronic autoimmune disease caused by perturbations of the immune system. The clinical presentation is heterogeneous, largely because of the multiple genetic and environmental factors that contribute to disease initiation and progression. Over the last 60 years, there have been a number of significant leaps in our understanding of the immunological mechanisms driving disease processes. We now know that multiple leucocyte subsets, together with inflammatory cytokines, chemokines and regulatory mediators that are normally involved in host protection from invading pathogens, contribute to the inflammatory events leading to tissue destruction and organ failure. In this broad overview, we discuss the main pathways involved in SLE and highlight new findings. We describe the immunological changes that characterize this form of autoimmunity. The major leucocytes that are essential for disease progression are discussed, together with key mediators that propagate the immune response and drive the inflammatory response in SLE.