Competition of the actions of antigen and polyclonal B-cell activator in the induction and amplification of B-memory cell function.

Using the capsular polysaccharide of Klebsiella pneumoniae (CPS-K) as a polyclonal B-cell activator (PBA) and sheep red blood cells (SRBC) as a T-dependent antigen, the correlation of the actions of PBA and T-dependent antigen on B cells in induction and amplification of immunological memory was studied. B-memory cell function, as judged by anti-SRBC responsiveness in vitro of spleen cells of CPS-K, was amplified by the secondary injection of SRBC into SRBC-primed mice, whereas it was decreased markedly by injection of CPS-K. When CPS-K was injected simultaneously with, or 1 or 2 days before the secondary injection of SRBC, B-memory cell function was also decreased markedly. On the other hand, CPS-K did not inhibit induction of B-memory cell function when injected simultaneouly with the primary injection of SRBC. However, CPS-K inhibited induction of B-memory cell function when injected 3 days before the primary injection of SRBC. The inhibition by CPS-K of amplification of B-memory cell function in response to SRBC when CPS-K was injected simultaneously with the secondary injection of SRBC occurred markedly in mice primed with SRBC 8 days or longer before the secondary injection, whereas it was not detectable in mice primed 3 days before. It is concluded that the CPS-K-mediated signal and the SRBC-mediated signal act competitively on the same subpopulations of B cells in induction and amplification of memory, and that the susceptibility of B cells to the CPS-K-mediated negative signal changes correspondingly with their maturation stage.