Blastogenic factor production by guinea pig B lymphocytes stimulated with thymus-dependent antigen

The purpose of the present paper is to determine whether antigen-stimulated B lymphocytes could produce blastogenic factor (BF) in the system of guinea pigs (strain 2) sensitized with keyhole limpet hemocyanin (KLH) or ovalbumin (OVA), known as thymus-dependent antigen, and, further, whether macrophages (M phi) are required for antigen activation of B cells to produce this lymphokine. Additionally, the effect of BF on normal T and B cells was evaluated. B lymphocytes were purified by double nylon wool adherence, plastic dish adherence. Sephadex G-10 column passage and sedimentation of E rosette forming cells on Ficoll-Isopaque. KLH- or OVA-primed B lymphocytes as well as T lymphocytes could produce BF when stimulated with specific antigen in vitro, and M phi were required for antigen activation of both T and B cells to produce BF. The optimal BF production was observed at a T or B cells: M phi ratio of 1:0.1 (in the system of KLH sensitization) or 1:0.5 (in OVA sensitization). BF production by B cells appeared to be less than that by T cells. BF produced by B cells was able to stimulate both normal T and B cells to proliferate; the proliferative responses of normal B cells to both B-cell-derived BF and T-cell-derived BF were significantly greater than those of normal T cells to these BFs. Readdition of M phi was not required for the T or B cell response to BF.