Ligation of the CD23, p45 (BLAST‐2, EBVCS) antigen triggers the cell‐cycle progression of activated B lymphocytes

Abstract CD23, p45 (BLAST‐2, EBVCS) is a 45‐kDa lineage‐restricted antigen which appears on the surface of human B cells shortly after activation. A monoclonal antibody (MHM6) to CD23, p45, as well as a polyclonal rabbit antibody raised against the purified antigen were found to promote DNA synthesis in purified tonsillar B cells which had been activated with phorbol ester. Interleukin 1, which was not, by itself, stimulatory for either resting or activated B cells, significantly augmented the growth‐promoting properties of MHM6. Kinetic studies indicated that while MHM6 exerted its influence in early G 1 , interleukin 1 acted later in the cycle just prior to the entry of cells into S phase. The findings demonstrate a role for CD23, p45 in triggering the progression of activated B lymphocytes through the G 1 phase of the cell cycle. The possibility that this antigen serves as a receptor for a B cell stimulatory factor is discussed.