Abstract
The immunological release of vasoactive amines from rabbit platelets by a mechanism requiring blood leukocytes has been described. The reaction involved leukocytes from an immunized rabbit, antigen, and platelets and did not require the complement system. The leukocytes appeared to be mononuclear, had the ability to adhere to glass, and were found in greater numbers in the blood than in spleen, lymph nodes, thoracic duct lymph, bone marrow, and peritoneal cavity washings.