F. N. J. Van Diepen

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.

Administration of OKT3 as a two-hour infusion attenuates first-dose side effects

BACKGROUND Use of the murine CD3 monoclonal antibody OKT3 is limited by first-dose side effects, which are thought to be caused by the release of inflammatory mediators. Because these processes might be influenced by the speed of administration, we compared a 2-hr OKT3 infusion with the bolus infusion usually applied nowadays. METHODS Eighteen renal allograft recipients were prophylactically treated with OKT3 and randomized to receive the first dose either as a 2-hr infusion or as an intravenous bolus infusion. Clinical side effects score and the occurrence of complement activation, cytokine release, and activation of neutrophils were determined. RESULTS Two-hour infusion of OKT3 completely prevented the occurrence of dyspnea, reduced the incidence of other side effects, and attenuated complement activation. Cytokine release and depletion of peripheral blood lymphocytes were similar in both groups. CONCLUSIONS Thus, complement activation seems to play an additional role in the development of side effects after the first OKT3 dose.

The CD8+ granzyme B+ T‐cell subset in peripheral blood from healthy individuals contains activated and apoptosis‐prone cells

Granzyme B (GrB) has been implicated in induction of apoptosis in target cells. The presence of GrB in peripheral blood CD8+ T cells from healthy individuals was analysed in immunocytochemical and flow cytometric studies. Furthermore, CD8+ GrB− T cells and CD8+ GrB+ T cells were compared regarding phenotypical characteristics and susceptibility to both spontaneous and Fas‐mediated apoptosis. GrB was expressed by approximately one‐fifth of CD8+ T cells. Compared with the CD8+ GrB− T‐cell subset, the CD8+ GrB+ T‐cell subset contained cells that were relatively more activated and more prone to spontaneous apoptosis. Culturing of cells with immunoglobulin M (IgM) anti‐Fas monoclonal antibody had no additional effect on the number of CD8+ GrB+ T cells undergoing apoptosis. We suggest that the presence of CD8+ GrB+ T cells in peripheral blood from healthy individuals results from immune surveillance or contact with infectious agents, and that spontaneous apoptosis of these cells might serve as a mechanism for their eventual clearance.