The fate of phytohaemagglutinin-activated human lymphocytes following their peak proliferative activity

Abstract

Following exposure to phytohaemagglutinin, lymphocytes in culture undergo a burst of proliferative activity lasting from the second to about the sixth day, after which mitosis ceases. The morphological changes accompanying lymphocyte activation and proliferation are well documented (Inman & Cooper, 1963; Douglas, Hoffman, Borjeson & Chessin, 1967; Chapman, Gough & Elves, 1967; Tokuyasu, Madden & Zeldis, 1968) but very little information is available about the subsequent fate of the cells and it is usually stated that after proliferation ceases the cells show indications of degeneration and eventually die (Bessis, 1973). However, the authors have observed that different cell types become evident in the later stages of cultures and several apparently healthy cells persist even after 17 days. The purpose of this study is to investigate the fine structure of the different cells which appear in the later stages of phytohaemagglutinin-stimulated lymphocyte cultures. This could shed light on the fate of activated lymphocytes after the phase of proliferation has ceased.