PHAGOCYTES Red Blood Cells

Oxidative stress has been implicated in the triggering of apoptosis in neutrophils. Because red blood cells (RBCs) are well known to scavenge oxidants including H2O2, we tested the hypothesis that RBCs inhibit apoptosis of neutrophils by reducing intracellular oxidative stress. Apoptosis of neutro-phils was evaluated by light microscopy and DNA gel electro-phoresis. We found that coculture with RBCs protected against neutrophil apoptosis. Neither physical contact be-tween RBCs and neutrophils nor the cellular integrity of RBCs was required to protect against neutrophil apoptosis. Neutrophil apoptosis was promoted by exogenous H2O2 but suppressed by catalase, indicating a role for H2O2 as a mediator of apoptosis. The protective effect of RBCs against apoptosis was due to catalase and glutathione metabolism because blocking of these antioxidant systems in RBC