Phospholipids inhibit cytotoxic effects of Actinobacillus actinomycetemcomitans leukotoxin on human polymorphonuclear leukocytes.

Isolated human peripheral blood neutrophils were exposed to sonic extracts of Actinobacillus actinomycetemcomitans. Such bacterial preparations contain a potent leukotoxin which rapidly kills the leukocytes as reflected by cellular uptake of trypan blue, extracellular release of lactate dehydrogenase, or discharge of 51Cr from pre-labeled cells. Exogenous phospholipids with a glycerol skeleton esterified by fatty acids or positively charged liposomes inhibited cytotoxic phenomena. The data suggest that cell damage may involve the interaction of leukotoxin with phospholipids in the neutrophil cell membrane and that exogenous lipids either compete for or sterically block binding of the leukotoxin to these moieties in the membrane.