Effect of interleukin-2 on CD95(Fas/APO-1) expression in fresh chronic lymphocytic leukaemia and mantle cell lymphoma cells : Relationship to ex vivo chemoresponse

Cells from B-cell chronic lymphocytic leukaemia (CLL) and mantle cell lymphoma (MCL) rarely express the CD95 (Fas/APO-1) antigen. Our aims were to determine whether CD95 levels (assessed by flow cytometry) in fresh neoplastic CD19+/CD5+ B-lymphocytes from CLL and MCL could be upregulated using clinically relevant doses of interleukin-2 (IL-2), and to compare this with their ex vivo cytotoxic drug sensitivity (assessed by DiSC assay). CD95-expression was absent/negligible in 13/14 CLL and 7/7 MCL specimens, Following culture (without IL-2) CD95 was expressed on dying CD5+ B-lymphocytes but only on live cells in 2/15 cases. In live cells from 2 CLL specimens, IL-2 caused up-regulation of CD95 and was associated with ex vivo drug resistance, Clinically relevant doses of IL-2 had pleiotropic effects on CD95-levels in fresh CLL cells, but did not induce CD95 in MCL cells. The link between CD95-induction and ex vivo drug resistance may point to a clinically resistant subset of CLL patients.