Abstract
Shedding of plasma membrane or ectocytosis is a ubiquitous process in eukaryotic cells. In this study, we examined the role of vesicles exfoliated from human peripheral blood leukocytes (PBL) in proliferation, expression of IL-2 receptor (CD25) and in the process of apoptosis (programmed cell death) in these cells. Vesicles derived from peripheral blood leukocytes stimulated with conconavalin (Con)-A induced agglutination, IL-2 receptor expression and proliferation in leukocytes freshly isolated from peripheral blood in a fashion similar to that induced by Con-A. These vesicles expressed Con-A on their surface. Furthermore, IL-2 receptor expression induced by concanavalin-A and by vesicles derived from Con-A activated PBL was inhibited by an antiserum to Con-A suggesting that the activation induced by vesicles is mediated by Con-A bound to their membranes. In contradistinction to these vesicles, those derived from IL-2 activated PBL, induced apoptosis in PBL freshly isolated from peripheral blood. The apoptotic leukocytes were identified by loss of cell viability, their distinct morphologic characteristics, and by reactivity with the monoclonal antibody, BM1 that reacts with apoptotic cells. These studies implicate vesicles shed from leukocytes in the proliferation, expression of IL-2 receptor and apoptosis of leukocytes.
