Mitogenic activity of water-soluble adjuvant obtained from Bacterionema matruchotii.

A butanol-extracted water-soluble adjuvant (Bu-WSA) obtained from Bacterionema matruchotii, a gram-positive oral bacterium, is a potent B-cell mitogen for murine lymphocytes in vitro. [(3)H]thymidine uptake of cultured spleen cells of BALB/c mice and nude athymic mice was greatly enhanced by the presence of Bu-WSA. Spleen cells which had been treated previously with rabbit anti-mouse thymocyte serum and guinea pig complement responded to Bu-WSA, whereas thymocytes and nylon wool column-filtered spleen cells were unresponsive to it. It was necessary for the adjuvant to be in the culture for at least 24 h in order to obtain significant lymphocyte activation. As macrophage-depleted spleen cells still responded to Bu-WSA, the proliferative response of lymphocytes seems to be independent of the presence of macrophages. The degree of response of spleen cells stimulated by a mixture of Bu-WSA and lipopolysaccharide (LPS) was very close to the sum of the responses stimulated by Bu-WSA and LPS individually. Spleen cells of LPS-injected mice, which were refractory to LPS, responded to Bu-WSA. On the other hand, the spleen cells of Bu-WSA-injected mice responded to LPS but not to Bu-WSA. Furthermore, the cells obtained from the spleens of mice which had been heavily cobalt 60 irradiated and bone marrow reconstituted 3 weeks in advance responded to LPS but not to Bu-WSA. Therefore, it appears that the cells responding to Bu-WSA were not identical to those responding to LPS.