STRAIN-SPECIFIC EXPRESSION OF MICROGLIAL KERATAN SULFATE PROTEOGLYCANS IN THE NORMAL RAT CENTRAL-NERVOUS-SYSTEM - INVERSE CORRELATION WITH CONSTITUTIVE EXPRESSION OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II ANTIGENS

We have recently demonstrated that a novel type of keratan sulfate pro teoglycan (KSPG) identified by the monoclonal antibody (mAb) 5D4 is ex pressed on ramified microglia but downregulated coincident with T-cell -mediated autoimmune inflammation of the spinal cord in Lewis (LEW) ra ts. In this study we show by immunocytochemistry and Western blot anal ysis that various inbred rat strains differ significantly in their con stitutive expression of KSPG on ramified microglia in the normal CNS. Microglial KSPG was high in LEW and Fischer 344 rats but low in DA, Br own Norway (BN), and PVG rats. The KSPG low-expressing strains exhibit ed constitutive expression of major histocompatibility complex (MHC) c lass II antigens on ramified microglia that was not detectable in the KSPG high-expressing strains. Thus, an inverse correlation between con stitutive KSPG and MHC class II expression was present. The KSPG-low-/ MHC class II-positive phenotype is associated with resistance to exper imental autoimmune encephalomyelitis in BN and PVG, but not DA rats. T hese findings suggest a significant impact of genetic factors on the m olecular differentiation of resident macrophages in the CNS. (C) 1996 Wiley-Liss, Inc.