Ultrastructural changes in guinea-pig bone marrow basophils during anaphylaxis

Abstract

A sequence of ultrastructural changes related to the degrees of severity of the anaphylactic reaction was observed in the bone marrow basophils of guinea-pigs. This sequence of changes might represent the sequential stages of a process of degranulation which consisted of (1) formation of haloes of low electron-density around the granules, (2) development of vacuoles by intercommunicating the adjacent haloes and of confluent vacuoles by joining the small vacuoles, and (3) disruption of cell membrane with concomitant expulsion of granules into the intercellular space or sinusoid. The vacuoles might communicate with the cisternae of the endoplasmic reticulum. Degranulation was found to be a result of an antigen—antibody reaction in which the reaginic antibodies produced had a selective affinity for the cell membrane of the basophils. The mechanism of degranulation might involve two factors: a physicochemical factor of changing the nature of the cell membrane resulting from the antigen—antibody interaction, and a mechanical factor of pressure exerted on the cell membrane by the confluent vacuoles. The alterations in the granules themselves, such as relatively larger size, lighter electron-opacity and looser texture, appeared to be associated with the histamine release from the granules. The structural changes of the granule contents encountered in anaphylaxis suggest that the ultrastructure of the basophil granules may be composed of an orderly interlacing framework of microfilaments onto which other constituent substances are bound.