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 a nd rapidly undergo apoptosis in vitro. The homologous Bcl-2 and Bar pr oteins have opposing effects, with Bcl-2 extending cellular survival a nd Bax promoting cell death following an apoptotic stimulus. We determ ined Bcl-2 to Bar expression ratios in peripheral blood lymphocytes, m onocytes and granulocytes and related them to the susceptibility of th ese cells to anti-Fas (anti-CD95)-induced apoptosis. Here, we show tha t Bax/Bcl-2 ratios are high in granulocytes and relatively low in mono cytes and lymphocytes, Furthermore, we show a relation between this ra tio in the different leucocyte subsets and their susceptibility to ant i-Fas-induced apoptosis, with granulocytes showing the highest suscept ibility, followed by monocytes and lymphocytes. It is concluded that t he balance between Bcl-2 and Bar forms an apoptotic rheostat, which se ems to determine sensitivity to apoptosis.