QUANTITATIVE CHARACTERIZATION AND POTENTIAL FUNCTION OF MEMBRANE FAS APO-1 (CD95) RECEPTORS ON LEUKEMIC-CELLS FROM CHRONIC B-LYMPHOID AND T-LYMPHOID LEUKEMIAS/

The expression and function of the Fas-receptor (Fas-R) were examined in chronic lymphocytic leukaemia (CLL), hairy cell leukaemia-variant ( HCL-v) and adult T-cell leukaemia (ATL). The expression of Fas-R in fr eshly isolated leukaemic cells was qualitatively and quantitatively di fferent between each disease; faint in B-CLL, moderate in HCL-v and st rong in ATL. Both full-length and alternatively spliced truncated form s of Fas mRNA were detected even in CLL B cells with faint to negative Fas-R, and Fas mRNA was also shown to be capable of increasing in vit ro expression, i.e. the message was functional, Ln contrast, Fas-R exp ression on ATL cells was heterogenous and usually intense with a mean density approximately 3-fold higher than that of normal T cells, Fas-R was confirmed to have the potential function for anti-Fas monoclonal antibody-mediated cell death in vitro in Fas-R+ ATL cells, The express ion level of Fas-R on the cells was higher in chronic than acute ATL ( 10360 v 6260 antibody-binding capacity per cell, mFas(ABC); P<0.05) an d was inversely correlated with serum LDH activity, suggesting that th e strong Fas-R accounts for the slow progression of chronic ATL and th e negative Fas-R protects from Fas-mediated cell death. These results show that Fas-R expression on leukaemic cells is valuable in their cha racterization and perhaps their function, and may contribute to the pr ogression and immune evasion of malignant clones.