Abstract
An in vitro proliferative system for immunoglobulin-G-forming plasma cells from the bone marrow of mice was established by the addition of antigenic protein and thymic cells or their homogenate to bone marrow cultures. The promoting activity of the thymus on plasma cells was independent from mouse strain, but it differed in strength with the variations of donor strains. Synthesis of immunoglobulin-G in proliferating plasma cells and its antibody reactivity against the administered antigen were demonstrated by immunocytological analyses.