Intact, 45-kDa (membrane) form of CD23 is consistently mitogenic for normal and transformed B lymphoblasts.
When isolated from lysates of the RPMI 8866 B lymphoblastoid cell line, the CD23 antigen was found to be present be in two forms corresponding to the intact 45-kDa membrane species and to a 25-kDa product that is more usually found as a released fragment in the extracellular medium. By contrast with preparations of extracellular species of CD23 which were seen to be variable in their biological activity, cell-associated CD23 was consistently mitogenic both for autogenous transformed B lymphoblasts and for pre-activated normal B cells. Addition to the normal cocktail of protease inhibitors of N alpha-tosyl-L-lysine chloromethylketone (TLCK), which has selectivity for trypsin-like serine proteases, resulted in preparations of CD23 from RPMI 8866 cell lysates that were exclusively in the 45-kDa intact form; such material retained full and reliable activity in the biological assays. The implications of these observations for the autocrine control of B lymphocyte growth are discussed.
Cairns
J A
JA
Department of Immunology, Medical School, Birmingham, GB.
Gordon
J
J
D015703:Antigens, CD / Q000302:isolation & purification / Q000502:physiology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000302:isolation & purification / Q000502:physiology*; D001402:B-Lymphocytes / Q000502:physiology*; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000502:physiology; D008970:Molecular Weight; D011961:Receptors, Fc / Q000302:isolation & purification / Q000502:physiology*; D017455:Receptors, IgE; D012995:Solubility
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D008562:Membrane Glycoproteins; D011961:Receptors, Fc; D017455:Receptors, IgE