Expression of a homologue of rat NG2 on human microglia

The expression of NG2 chondroitin sulfate has been widely associated with o ligodendrocyte precursors in rodents. We used a monoclonal antibody (9.2.27 ) against the human homologue of the rat NG2 to determine whether expressio n of this molecule was associated with a specific glial cell population pre sent in dissociated cell preparations derived from adult and fetal human br ain tissue. Our data, derived using FAGS and immunocytochemical analyses of immediately ex vivo or cultured glial cells, indicate that the large major ity of NG2 expressing cells belonged to the microglial lineage (CD68, CD11c ) rather than to the oligodendrocyte lineage (O4, A2B5, GalC). In situ immu nohistochemistry performed on non-fixed normal spinal cord tissue confirmed the observation that NG2 is expressed by mononuclear phagocytes of the CNS . In contrast, peripheral blood-derived monocytes were NG2(-). Cells from f etal brain tissue showed only small numbers of NG2(+) cells, which was cons istent with the number of microglial cells in this preparation. In absence of additional markers, we cannot exclude that this anti-NG2 mAb might also recognize human oligodendrocyte progenitor cells. GLIA 27:259-268, 1999. (C ) 1999 Wiley-Liss, Inc.