| Abstract: | There is a strong stimulation of the primary immune response when spleen cells of the CBA/H and CBA/J strains of mice are cocultured in the Mishell-Dutton system and stimulated with foreign erythrocytes or hapten-erythrocyte conjugates. This stimulation occurs regardless of carrier (sheep red blood cells) priming of one donor of the spleen cells. The enhancement of the primary immune response is most evident early in the course of the immune response. During mixed spleen cell culture, cells of the CBA/H strain can recognize and proliferate in response to CBA/J spleen cells, but not vice versa. When CBA/H spleen cells are cultured with irradiated CBA/J spleen cells, there is a strong stimulation of the immune response of the B cells of the CBA/H strain even though they are bystanders to the ensuing allogeneic response. Supernatants of 20-hour cultures of mixtures of CBA/H and CBA/J spleen cells restored the immune responsiveness of spleen cells from nu/nu mice. The generation of this B cell stimulatory activity is dependent on the presence of Θ-bearing cells of CBA/H origin during the 20-hour culture. These findings are consistent with the release of a B cell stimulatory activity from mixtures of spleen cells of mice which differ at a locus associated with a mixed lymphocyte response which is not linked to the H-2 gene complex (M locus). |
