Are mitogenic sera necessary for the generation of human plaque-forming cells?

Human plaque-forming cells (PFC) have been quantitated following pokeweed mitogen stimulation by a protein A plaque technique using human erythrocytes. The PFC are generated in cultures supplemented with non-mitogenic human AB serum or foetal bovine serum (FBS) of varying degrees of inherent mitogenicity. In the latter case, no correlation exists between the mitogenicity of the serum supplement used in these cultures and the PFC response obtained. This fact, in addition to the demonstrated usefulness of the AB sera in facilitating the generation of PFC makes it unlikely that serum mitogenicity is a requirement for in vitro human immunoglobulin synthesis and secretion.