Modulation of B Cell Stimulation by Maternal Serum

Anti-IgM stimulation of B cells is decreased in the presence of maternal serum as compared to control media. This inhibiting influence of maternal serum is observed during the priming of the B cells. The progression of B cells into cellular proliferation was not influenced by maternal serum. At the level of the immunoglobulin secretion, the influence of maternal serum was also shown. A significant down regulation of the IgM, no change of the IgG production, and an enhanced secretion of IgA and IgE was demonstrated in the presence of maternal serum as compared to control media. It has been suggested that the maternal IgG fraction contains a molecule partly responsible for these changes. Furthermore, the CD23 antigen is increased when B cells are stimulated in the presence of a pool of maternal IgG. All the findings concerning maternal IgG were more pronounced when retroplacental IgG was used instead of peripheral maternal IgG. This observation suggests that the factor responsible for the B cell changes is released at the fetomaternal interface.