Activated B cells express receptors for, and proliferate in response to, pure interleukin 2.

Abstract

Whether interleukin 2 (IL-2) acts on B cell proliferation and whether activated B cells express IL-2 receptors was investigated. The functional activity of immunoaffinity-purified or recombinant human IL-2 was studied in a B blast assay using positively selected murine surface Ig-positive cells that had been activated by lipopolysaccharide (LPS) plus anti-Ig antibodies (anti-Ig). In this assay, T cells were not detected by fluorescence-activated cell sorter analysis. Both IL-2 preparations led to optimal B cell proliferative compared with supernatants obtained from murine or human spleen cells or murine cloned T helper cells. The IL-2 requirement was about the same as in a proliferation assay using lectin-activated polyclonal murine Lyt-2-positive T cells. Analysis of the binding of radiolabeled immunoaffinity-purified IL-2 to B cells indicated that LPS plus anti-Ig-activated B cells expressed a mean of 3,500 IL-2 receptors per cell with an apparent dissociation constant of 150 pM. Neither nonactivated B cells nor B cells activated by LPS alone exhibited significant specific IL-2 binding. IL-2 is apparently a growth factor not only for T cells but also for B cells.