The induction and regulation of guinea pig B-lymphocyte proliferation in vitro.

Conditions for the in vitro induction of proliferation have been examined in a population of guinea pig lymph node lymphocytes enriched for B lymphocytes. Known B cell mitogens such as bacterial lipopolysaccharide and tuberculin-purified protein derivative induced DNA synthetic responses in this B lymphocyte population as did a number of dinitrophenyl hapten-protein conjugates, all in the apparent absence of T cell participation. B cell proliferation occurred most efficiently in serum-free medium with both heterologous and homologous sera inhibiting maximum responses. In vivo immunization with hapten-protein conjugates failed to enhance subsequent in vitro B cell responsiveness to these materials beyond that owing to recruitment by contaminating antigen-primed T cells. Macrophage-associated antigen, which efficiently triggered T cell proliferation was much less effective at initiating B cell DNA synthesis than was soluble antigen not bound to macrophages. Furthermore, although accessory cells were required for the development of T cell DNA synthetic responses, macrophages of factors produced by them inhibited spontaneous or induced B cell 3H-thymidine incorporation.