Studies of the mechanism of antigen stimulation of DNA synthesis in rabbit spleen cultures.

The uptake of [C]thymidine by spleen cell suspensions from rabbits previously immunized to heterologous proteins is stimulated by spleen and peritoneal exudate cells containing the antigen. The stimulation is specific and dependent on cell contact mediated by surface antigen. It represents an increased rate of DNA synthesis and cell division by cells with the characteristics of undifferentiated cells. Macrophages become surrounded by non-dividing lymphocytes during the early period of culture and it is postulated that this reaction results in enhancement of DNA synthesis by responding cells, with the small lymphocytes acting as messengers between cells containing antigen and those dividing in response to its presence.