Manganese induces apoptosis of human B cells: caspase-dependent cell death blocked by bcl-2.

Manganese ions block apoptosis of phagocytes induced by various agents. The prevention of apoptosis was attributed to the activation of manganous superoxide dismutase (Mn-SOD) and to the antioxidant function of free Mn2+ cations. However, the effect of Mn2+ on B cell apoptosis is not documented.

Respiratory burst in human B lymphocytes. Triggering of surface Ig receptors induces modulation of chemiluminescence signal.

B lymphocytes have been shown to proliferate and release oxygen metabolites when surface Ig is cross-linked and when stimulated with phorbol ester. Biochemical evidence has been provided for the presence of a superoxide generating system in B cells, which seems to be identical to the well-characterized NADPH-oxidase of phagocytes. In this report, we show that normal and EBV-transformed B cells produce superoxide anions after stimulation with phorbol ester and when surface Ig was cross-linked, as detected by lucigenin-dependent chemiluminescence.

T-cell chemiluminescence. A novel aspect of T-cell membrane activation studied with a Jurkat tumour cell line.

The binding of mitogenic lectins phytohaemagglutinin (PHA), concanavalin A (Con A) and/or of monoclonal antibodies to different receptors such as antigen receptor complex or CD2 on human T cells generates increases in the concentrations of inositol triphosphate (IP3) and cytoplasmic free calcium. This T lymphocyte requires the delivery of two signals; the first can be provided by specific monoclonal antibodies or by mitogenic lectins, and the second by a phorbol ester, phorbol myristate acetate (PMA). In other cells such as macrophages, the rise of intracellular calcium via the generation of IP3 and stimulation of protein kinase C can activate the phospholipase A2, a calcium-dependent enzyme.