Observations on the discharged granules from guinea-pig bone marrow basophils following anaphylaxis.

Degranulation of basophils took place in sensitized guinea-pigs when challenged with specific antigen, regardless of whether the animals had received a mepyramine maleate (anti-histamine) injection or not. The degranulation was most pronounced in the first 5 minutes following challenge. The discharged basophil granules were taken up by the neutrophils, the macrophages, and the monocytes in the bone marrow; the neutrophils, however, responded much more promptly and actively than the other phagocytes. Phagocytosis of the discharged basophil granules was most active 10–15 minutes following challenge, during which varying numbers of phagocytic vacuoles were found in the phagocytes. Stages of changes were observed in the phagocytic vacuoles and their granule contents, which consisted of: (1) diminution or disappearance of the perigranular clear space with subsequent adhesion of the limiting membrane of the vacuole to the granule content; (2) disintegration or dissolution of the granule content and the limiting membrane of the vacuole; and (3) incorporation of the granule content into the cytoplasmic matrix of the phagocyte. In addition, a depletion of neutrophil granules in the cytoplasm surrounding the phagocytic vacuole was also observed in association with the above changes, and was suggested to be related to the digestion of the ingested granules. The discharged basophil granules disappeared completely from the bone marrow by 1 hour after challenge. The removal of the granules was by digestion while they were in the bone marrow as well as by dispersal of the granules through the bone marrow sinusoids into the circulation.