Abstract
Summary The PCA reaction induced m rats with hyperimmune antibody, whether homologous or heterologous, was suppressed in leukopenic and partially leukopenic animals but was not suppressed by pretreatment of the animals with antihistamine and anti-serotonin. Mast cells did not appear to be primarily involved in the reaction. Ultra-structural observations showed that PMN-leukocytes in the lesions had phagocytosed micro-precipitates of antigen and antibody and subsequently degranulated. Based on these observations, it is suggested that PCA produced with hyperimmune antibody in the rat is mediated by release of lysosomal material from PMN-leukocytes.