The effect of haemopoietic stem cell proliferation on the humoral immune response in mice.

A study was made of the effect of humoral factors, isolated from bone marrow cell (BMC) supernatant fluid and capable of modifying CFU-S proliferation, on the generation of IgM plaque-forming cells (PFC) against sheep red blood cells (SRBC) in mice after adoptive transfer. Adoptive transfer of BMC, preincubated with the humoral factor RBME-III, which stimulates CFU-S proliferation, was shown to suppress the splenic PFC generation in recipients; treatment of BMC with a further factor NBME-IV, which inhibits CFU-S proliferation, was followed by augmentation of PFC generation. Similar effects were obtained while studying the IgM PFC generation in the bone marrow of mice after secondary immunization when relevant factors were injected, in vivo, 24 hr following primary immunization. The results of adoptive transfer experiments indicate that populations of T- and B-cells are not the targets for the action of CFU-S proliferation regulatory factors. These factors are shown to modulate the erythroid differentiation of CFU-S. The possibility of quantitative modification of immune response parameters with the help of bone marrow factors that influence the proliferation and differentiation of CFU-S is discussed.