Blood Platelets in Anaphylaxis

Abstract

Summary A significant decrease in the number of blood platelets was found upon reinjecting antigen intravenously into sensitized monkeys. No such decrease occurred in normal nonsensitized monkeys, although the same or larger amounts of antigen were injected. In general the diminution in blood platelets paralleled the degree of shock. In desensitized monkeys, the blood-platelet counts diminished progressively with each injection of antigen in spite of the fact that subsequent reactions were mild or negative. Monkeys injected with Witte peptone or histamine phosphate in amounts large enough to produce shock failed to show any significant change in the number of blood platelets. Results similar to those observed in monkeys were obtained in guinea pigs actively sensitized with egg-white or horse serum. Guinea pigs sensitized with crystalline ovalbumin showed no decrease in blood-platelet count when shocked with the same antigen (except in one instance of delayed reaction) but did show a decrease when shocked with egg-white. Histamine shock was without effect. Guinea pigs passively sensitized with anti-egg white or anti-crystalline ovalbumin rabbit serum showed a significant decrease in blood platelets when shocked with the appropriate antigen. Rabbits repeatedly injected with crystalline ovalbumin and given a test-dose of the same antigen one week later showed a moderate decrease in blood platelets although there was no clinical evidence of anaphylactic shock.