Expression of surface membrane IgG on pokeweed mitogen-reactive anti-tetanus toxoid antibody-producing cells.

Anti-tetanus toxoid antibody-producing cells, differentially expressing surface membrane IgM, were analyzed for the additional expression of surface membrane IgG. micron+ and micron- cells were rosetted with anti-gamma-ox red blood cells and separated by density centrifugation into fractions enriched or depleted of gamma + cells. These B-cell subsets were assayed for the production of IgM and IgG anti-tetanus toxoid antibody and total IgM and IgG. The results indicated that the majority of anti-tetanus toxoid antibody synthesis in the micron- fraction was by gamma + cells. In the microm+ fraction, however, both IgM and IgG anti-tetanus toxoid antibody production was detected in the micron+ gamma- and micron+ gamma+ fraction. The inclusion of isotype-specific antisera during the first 2 days of culture further established that gamma was expressed on the surface of the majority of the precursors for IgG anti-tetanus antibody production in vitro. Studies performed to determine the culture requirements of micron- and micron+ cells revealed that production of IgG anti-tetanus toxoid antibody by both cell subsets was dependent on T cells and pokeweed mitogen. However, some micron- cells could produce IgG in the presence of T cells alone.