Structural and functional characterization of IL 2 receptors on activated human B cells.

After activation, B cells express the IL 2 receptor as determined by their reactivity with monoclonal anti-IL 2 receptor antibodies. In this report we show that anti-IL 2 receptor antibodies precipitated comparable 60,000 to 65,000 dalton proteins from highly purified B and T cells. Limited peptide mapping suggested that the receptors on B and T cells were identical. Moreover, activated B cells could be induced to proliferate by IL 2, but not to secrete Ig. Anti-IL 2R antibody blocked the effect of IL 2 but not the proliferative response induced by B cell growth factor (BCGF), suggesting independent growth factor receptors. Investigation of the kinetics of the B cell response to growth factor indicated that BCGF acts within 24 hr, whereas IL 2 was virtually devoid of activity for 48 hr. Nevertheless, after 72 to 96 hr, the effect of IL 2 was equal to or greater than that obtained with BCGF. These studies suggest that the initial stages of B cell proliferation involves a sequential interaction of BCGF and IL 2 with their respective receptors.