Inhibition of macrophage response to brain injury. A new effect of pertussis vaccine possibly related to histamine-sensitizing factor.

Intravenous injection of pertussis vaccine inhibited the outpouring of macrophages into a zone of thermal coagulation necrosis in the brain. The inhibition of this cellular reaction to injury was observed in rats and mice, and was especially notable in gerbils. It was not due to nonspecific stress or to endotoxin. A relationship of this new activity to pertussis vaccine's histamine-sensitizing factor was suggested by the use of partially purified extracts and heat-inactivated vaccines. There was a close parallel between the effects of pertussis vaccine on brain macrophages and on the spleen.