THE FAS ANTIGEN (CD95) ON HUMAN LYMPHOID-CELLS - EPITOPE ANALYSIS WITH 10 ANTIBODIES

The expression of CD95 antigen was examined on adult and cord blood ly mphocytes using a highly sensitive immunofluorescence/flow cytometric procedure. CD95 was expressed by the majority of circulating blood T c ells in adults, and by a smaller proportion of CD4+ and CD8+ T cells i n cord blood. The majority of circulating B cells did not react with s even CD95 antibodies, but three antibodies did stain B cells. In tonsi l sections, CD95 was expressed throughout the tissue, but germinal cen tres showed, generally stronger staining than the surrounding follicul ar mantle and interfollicular areas. This was confirmed by flow cytome try, which showed expression preferentially on B cells with a germinal centre phenotype. Because different antibodies stained different prop ortions of B cells, CD95 epitopes were examined by inhibition, additiv e binding and protease susceptibility studies using a panel of ten CD9 5 antibodies. B cells apparently reacting selectively with CD95 antibo dies were sorted and CD95 mRNA was reverse transcribed to cDNA and ana lyzed, in order to confirm the presence of CD95 in cells which reacted selectively and to explore the possible existence of CD95 isoforms. T he major cDNA band was identical in the two populations. Inhibition of N-glycosylation suggested a that the epitopes detected differentially could not be accounted for by differential N-glycosylation.