Interaction of lipoteichoic acid of group A streptococci with human platelets

Publisher Website
Google Scholar
Abstract
The interaction of group A streptococcal lipoteichoic acid (LTA) [which may be associated with streptococcal pathogenicity or immunotoxic reactions during streptococcal infections] with mammalian cell membranes was studied in human platelets. The binding of LTA to platelets was platelet concentration and time dependent. Binding approached a maximum within 10 min of incubation. The bound LTA could be displaced by adding a 50-fold excess of unlabeled LTA. An association constant of 1.9 .times. 10-7 M was calculated, and only 1 population of binding sites was detected. Immunoferritin labeling of LTA-treated platelets demonstrated a patchy distribution of LTA binding sites on the platelet surface. LTA inhibited collagen- and .alpha.1 chain-induced platelet aggregation, but not the platelet release reaction, suggesting that the LTA and collagen binding sites on human platelets are distinct. Apparently, LTA binds to platelets and interferes with collagen-induced aggregation although collagen is still able to attach to binding sites to trigger the release reaction.