The absolute requirement for T-cells in the induction of IgM-secreting cells, in vitro.

Anti-rabbit thymocyte antibody can totally inhibit the induction of IgM production that ordinarily is observed whem lymphoid cells are incubated, in virto, in the absence of added antigen. Univalent as well as bivalent antithymocyte antibody preparations were inhibitory when added to cells before the induction of immunoglobulin production had occurred but not afterwards. Spleen cells that had been treated with antithymocyte antibody and then cultured with thymocytes for 72 hours exhibited an enhanced inducttion of immunoglobulin production. Untreated spleen cells also showed this property, although both untreated lymph node cells and lymph node cells treated with antithymocyte antiboyd did not respond to thymocytes. The enhancement of the induction of immunoglobulin production by lipopolysaccharide was found to be T-cell dependent as judged from studies using antithymocyte antibody.