Inhibition of apoptosis in polymorphonuclear neutrophils from burn patients

Normal human polymorphonuclear neutrophils (PMN) undergo rapid apoptosis during in vitro culture. In contrast, apoptosis is inhibited in PMN from patients with severe burns. This inhibition is not an inherent property of the cells but is caused by thermolabile factors present in the plasma. Endotoxin and the proinflammatory cytokines interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) do not appear to be directly responsible. The ability of burn plasma to inhibit apoptosis was reduced by neutralizing antibodies to human granulocyte macrophage colony-stimulating factor (GM-CSF). GM-CSF levels could not be detected in the burn plasma. However, the incubation of burn-derived or normal leukocyte populations consisting primarily of PMN in burn plasma induced the production of GM-CSF. The results suggest that activation of GM-CSF synthesis by factor(s) in burn plasma may play a role in regulating inflammation by the inhibition of apoptosis.