Quantification of Bax/Bcl‐2 ratios in peripheral blood lymphocytes, monocytes and granulocytes and their relation to susceptibility to anti‐Fas (anti‐CD95)‐induced apoptosis
Neutrophils have the shortest half‐life among circulating leucocytes and rapidly undergo apoptosis in vitro. The homologous Bcl‐2 and Bax proteins have opposing effects, with Bcl‐2 extending cellular survival and Bax promoting cell death following an apoptotic stimulus. We determined Bcl‐2 to Bax expression ratios in peripheral blood lymphocytes, monocytes and granulocytes and related them to the susceptibility of these cells to anti‐Fas (anti‐CD95)‐induced apoptosis. Here, we show that Bax/Bcl‐2 ratios are high in granulocytes and relatively low in monocytes and lymphocytes. Furthermore, we show a relation between this ratio in the different leucocyte subsets and their susceptibility to anti‐Fas‐induced apoptosis, with granulocytes showing the highest susceptibility, followed by monocytes and lymphocytes. It is concluded that the balance between Bcl‐2 and Bax forms an apoptotic rheostat, which seems to determine sensitivity to apoptosis.