IL 1 requirement for B cell activation revealed by use of adult serum.

Fetal calf serum is an essential component of the culture medium developed by Mishell and Dutton for the immunization of murine spleen cells in vitro. Serum from adult donors (mouse, human, rabbit) does not support antibody synthesis in this system. This "deficiency" of adult serum can be overcome with IL 1. Adult serum in the presence of IL 1 is as effective in stimulating a B cell response against xenogeneic red cells as fetal calf serum. We attribute the capacity of fetal calf serum to support an immune response in the absence of exogenous IL 1 to serum factors that cause macrophages to release IL 1 endogenously. Our findings strengthen the notion that IL 1 plays an essential role in the process of B cell activation and suggests that the use of fetal calf serum should be avoided in studies concerned with the function of interleukin 1.