Immunologic differences in murine glial cells and their association with susceptibility to experimental allergic encephalomyelitis

Neuroprotection by IL-10-producing MOG CD4+ T cells following ischemic stroke

Mucosal tolerance has been used successfully to treat animal models of autoimmune diseases and is being tested in human diseases. In this work we demonstrate the reduction of infarct size following mucosal tolerance by myelin oligodendrocyte glycoprotein (MOG) (35-55) peptide in mouse stroke model. Nasal MOG was most efficacious and reduced ischemic infarct size by 70% at 24 h as well as improving behavior score. Using immunohistological methods and IL-10 -/- mice, we demonstrate the importance of IL-10-producing CD4+ T cells in the reduction of the ischemic infarct volume following middle cerebral artery occlusion (MCAO). Furthermore, adoptive transfer of CD4+ T cells from nasally tolerized mice to untreated mice prior to MCAO surgery significantly decreased stroke size (p<0.001 vs. control), whereas CD4+ T cells from nasally tolerized IL-10-deficient mice had no significant effect. Based on these results, modulation of cerebral inflammation by mucosal tolerance to myelin antigens may have applicability both as prophylactic therapy and treatment following ischemia attacks.

Differential selectivity of CIITA promoter activation by IFN-gamma and IRF-1 in astrocytes and macrophages: CIITA promoter activation is not affected by TNF-alpha

During demyelinating disease of the central nervous system (CNS), locally elevated cytokine levels may induce upregulation of MHC class II molecules on otherwise low expressing or negative cell types such as microglia and astrocytes, since IFN-gamma has been shown to induce MHC class II expression on these cell types in vitro. While many transcription factors are involved with MHC class II expression, only the class II transactivator (CIITA) is tightly coordinated with IFN-gamma-inducibility. Control of CIITA gene expression is complex, involving four distinct promoters, two of which (promoters III and IV) are IFN-gamma-inducible in certain cell types. Here we demonstrate that IFN-gamma treatment of rat astrocytes induces only CIITA promoter IV activity in contrast to the murine macrophage cell line RAW 264.7 that uses both IFN-gamma-inducible promoters. In contrast to previously published reports, promoter IV activation is completely dependent upon an intact interferon regulatory factor-1 (IRF-1) but not STAT binding site using promoter constructs specifically mutated at these positions. Importantly, while TNF-alpha is able to synergize with IFN-gamma to increase astrocyte MHC class II expression in vitro, we show that treatment of rat astrocytes with TNF-alpha has no effect on CIITA promoter activity. These data demonstrate that TNF-alpha augments MHC class II expression through a mechanism downstream or independent of CIITA induction.

Interferon-gamma-inducible endothelial cell class II major histocompatibility complex expression correlates with strain- and site-specific susceptibility to experimental allergic encephalomyelitis

The interaction between encephalitogenic lymphocytes and the cerebral microvascular lining is considered to be an important initial step in the recruitment of immune cells into the central nervous system (CNS) under pathological conditions such as multiple sclerosis (MS) and its investigative analog, experimental allergic encephalomyelitis (EAE). This study was conducted in order to examine whether differences in microvascular endothelial cell expression of several molecules involved in lymphovascular interactions correlate with the strain and organ-specific development of EAE. Cerebral and epididymal microvascular endothelial cells (EC) were isolated from SJL and B10.S mice, which, despite MHC-compatibility (H-2S), differ in their ability to develop EAE. The subcultured cells were then analyzed by flow cytometry for their ability to express class I MHC, class II MHC and ICAM-1 molecules in response to treatment with murine recombinant interferon-gamma (IFN-gamma). Over a range of doses and times, cerebral EC cultures derived from EAE-susceptible SJL mice expressed two-fold higher levels and higher cell surface densities of class II molecules than cerebral EC cultures derived from EAE-resistant B10.S mice, whereas class I and ICAM-1 molecules were comparably upregulated on both SJL and B10.S cerebral EC. In contrast, both SJL and B10.S epididymal EC cultures expressed lower but comparable levels of class II molecules in response to IFN-gamma. Class I and ICAM-1 molecules, however, were upregulated to at least the same degree as that observed on cerebral EC derived from both strains.(ABSTRACT TRUNCATED AT 250 WORDS)

Major histocompatibility complex molecules on glial cells

While glial cells of the central nervous system do not constitutively express class I or II major histocompatibility complex (MHC) molecules, astrocytes and microglial cells can be induced by a variety of factors to express these antigens. Oligodendrocytes have inducible class I but not class II elements. There are considerable differences in regulation of MHC antigen expression between glial cells from rodent and human brains, both in situ and in vitro. The consequence of glial cell MHC expression for immune interactions in the CNS is discussed in the context of glial cell antigen presentation capacity and neural cell susceptibility to cell-mediated immune effector mechanisms.

Autoimmune inflammation of astrocyte transplants

Astrocytes have been shown to be capable of serving as antigen-presenting cells and as targets for encephalitogenic cytotoxic T lymphocytes. The role of astrocytes in central nervous system (CNS) autoimmune inflammation is unclear. To study this further, we transplanted astrocyte aggregates into the anterior eye chamber of the mouse. The astrocytic nature of these transplants was confirmed by immunohistochemical detection of glial fibrillary acidic protein and the inability to detect oligodendrocyte or microglial markers. When mice bearing transplants were induced to develop experimental allergic encephalomyelitis by either passive or active protocols, the astrocyte transplants developed a perivascular inflammatory response similar to that seen in the host CNS during the course of the encephalomyelitis. The data suggest that astrocytes could serve as targets for the autoimmune attack of experimental allergic encephalomyelitis and support the possibility that the pathogenesis of this disease may involve an autoimmune reaction against a site other than the myelin sheath.