Inhibition of induction of apoptosis in K562 cells and in CCRF-CEM cells by anti-β₂m MoAb. (A) β₂m-induced apoptosis in K562 cells was suppressed by the addition of 100 μg anti-β₂m MoAb derived from hybridoma clone NK2. Anti-β₂m MoAbs (clone NK1 and NK3) were the negative controls at the same concentration. (B) β₂m-induced apoptosis in CCRF-CEM cells was suppressed by preincubation with anti-β₂m MoAb (clone NK2). Apoptotic cells were assayed by TUNEL. Data are expressed as the mean ± SE of 3 independent experiments. (C) The effects of anti-β₂m MoAbs for the interaction of biotinilated β₂m and the cell surface on CCRF-CEM cells were analyzed using FACS (dotted line, control; thin line, no additive of anti-β₂m MoAb; thick line, additive of anti-β₂m MoAb).