Primary encounter with antigen stimulates specific B cells not only to differentiate into cells that produce antibody at a high rate (plasma cells), but also to give rise to populations of memory cells. These cells have many characteristics that differ from virgin B cells, including their lifespan. When re-exposed to antigen, memory cells generate secondary IgG responses that are enhanced in rate, titre and affinity. At present they are considered as small resting lymphocytes which survive for long periods in a quiescent state between each antigen encounter. However, the fact that an individual may continue to make an antibody response for many months following a single injection of antigen is often overlooked. This continued antibody production is probably due to repeated stimulation of antigen-specific B cells and raises the question of whether memory B-cell clones require antigen for their maintenance. Here we show that they do, and that following transfer, in the absence of antigen, memory B-cell populations are lost from the adoptive host after 10-12 weeks.

No abstract

No 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).

No abstract