Studies on the generation of B lymphocytes in the mouse embryo

Using an organ culture technique, the development of B lymphocytes has been studied in a number of isolated embryonic hemopoietic tissues. Developing B lymphocytes were identified by cytoplasmic and surface immunofluorescence using purified class-specific antibodies and a Fab anti-immunoglobulin reagent. In fetal liver cultures these cells were further characterized for Fc and complement receptors and for the presence of mouse-specific B lymphocyte antigen. The results indicate that B lymphocytes develop independently in fetal liver and in fetal spleen; they do not develop in cultures of yolk sac and thymus. In conclusion, it is likely that B lymphocyte maturation in mammals is multifocal and is not dependent upon gastrointestinal influences as suggested previously.