Petechial hemorrhages in the small intestinal Peyer's patches: a new manifestation of systemic anaphylaxis.

Systemic anaphylaxis in the rat has major manifestations in the small intestine. In August rats, but not in other strains, intestinal anaphylaxis was accompanied by petechial hemorrhages in Peyer's patches. The occurrence of petechiae was not proportional to the intensity of prostration, cyanosis or gut congestion. No hemorrhages were found in other organs. The petechiae occurred in August rats of either sex after sensitization and challenge with any of several antigens and adjuvants and after passive sensitization with antiserum. The number of Peyer's patches with hemorrhage varied from one to all 20 in individual rats. The occurrence of petechiae was not influenced significantly by the route of sensitization or challenge, by the presence or absence of pinworms in the cecum, or by ancillary treatment at time of challenge with normal serum, normal blood, heparin, pertussis vaccine or lipopolysaccharide. The intestinal mast cells of the susceptible August rats were not different from the mast cells of the resistant strains. Furthermore, mast cells did not reside in the lymphoid follicles of Peyer's patches which was the site of the petechial hemorrhages in anaphylactic August rats. Nor did injections of histamine, serotonin or both cause hemorrhages in Peyer's patches.