Dissociation of interleukin 2‐dependent and ‐independent B cell proliferation with monoclonal anti‐interleukin 2 receptor antibody

In a recent report from our laboratory (J. Exp. Med. 1984. 160: 1070), it has been shown that B cells which have been activated with lipopolysaccharide (LPS) plus anti-Ig antibodies express interleukin 2 (IL2) receptors and proliferate in response to pure IL2. In the present study, we have investigated the role of IL2 during proliferative B cell responses supported by various T cell supernatants (SN) as well as by LPS itself. The following results were obtained: (a) B cells activated with LPS plus anti-Ig were found to proliferate in response to either recombinant IL2, T cell SN or fresh LPS; (b) a monoclonal anti-IL2 receptor antibody (PC61) could completely inhibit the effects of recombinant IL2 or various T cell SN (cloned T helper cell SN, EL4 SN, concanavalin A-spleen cell SN or mixed leukocyte culture SN), but did not interfere with the effect of LPS; (c) B cells activated with LPS or LPS plus anti-Ig were not found to secrete detectable amounts of IL2 by themselves. Thus, the data demonstrate that LPS-stimulated B cell proliferation requires neither B cell autocrine nor T cell-derived IL2. On the other hand, with regard to LPS plus anti-Ig-activated B cells, IL2 appeared to be the only growth-promoting activity that could be detected in the supernatants obtained from total normal spleen cell populations.