Antigen requirements for priming of IgG producing B memory cells specific for Type III pneumococcal polysaccharide.

B cells from mice primed with various amounts of the T-independent (TI) antigen Type III pneumococcal polysaccharide (S3) or with the T-dependent (TD) form of S3, i.e. S3-HRBC, were transferred to irradiated recipients with T cells from S3-HRBC primed mice. After immunization with S3-HRBC, significant S3-specific IgG memory responses were produced only by those mice which received B cells from mice primed with the TD antigen. Activation of amplifier T cells (TA) at the time of priming with S3 resulted in increased IgG production by transferred B cells although the amount of IgG produced was still substantially less than that produced by B cells from S3-HRBC primed mice. An amount of S3 (0.6 microgram) which induces optimal primary IgM responses was found to suppress the induction of B memory cells by S3-HRBC. Lower amounts of S3 were not suppressive yet they were still unable to induce IgG memory in B cells. Taken together the results suggest that the TI antigen S3 does not induce differentiation of B cells to IgG producing memory cells because S3 is unable to activate a cell type (presumably T helper cells) which is required for this inductive process to occur.