The Proliferation of Plasma Cells from Mouse Bone Marrow in Vitro III. Primary and Secondary Immune Responses Associated with Thymic RNA

In vitro primary and secondary immune responses involving the proliferation of IgG-forming plasma cells from cultures of normal or antigen-primed mouse bone marrow cells have been investigated in order to clarify the relationships between the bone marrow cells and thymic RNA derived from each animal. By an administration of soluble and insoluble antigens with thymic RNA to bone marrow cultures, 54 ± 13% of IgG-forming plasma cells were found to produce specific immunoglobulin following stimulation with antigen. Thymus independent antigen polyvinylpyrrolidone (PVP) induced the proliferation of anti-PVP specific antibody forming cells in the abcence of thymic RNA, although more of these cells were generated when PVP-primed thymic RNA was administered with PVP to normal bone marrow cultures. Other antigens such as keyhole limpet hemocyanin (KLH), flagellar antigen of Salmonella, apofferitin and SRBC were investigated using the same bone marrow culture system. These antigens induced various numbers of antibody forming cells from the cultures. Antigen-primed thymic RNA derived from mice inoculated with antigen caused secondary immune response-patterns of plasma cell proliferation from normal bone marrow cultures. Bone marrow cells, however, derived from antigen primed animals proliferated with patterns of primary immune response when cultured with normal thymic RNA and the same antigen. On the basis of these observations, it is concluded that anamnestic immune memory is mainly associated with thymic RNA and not with immunoblasts in bone marrow.