Abstract
The addition of sheep antisera to rabbit IgG or to rabbit IgG subunits (L chain, H chain, Fab piece, Fc piece) to in vitro cultures of rabbit peripheral lymphocytes may induce up to 80-90% of the small lymphocytes to transform into immature "blast" cells. As many as 1 x 107 molecules of antibody may be required to stimulate each cell. Each peripheral lymphocyte carries the antigenic specificities of the entire IgG molecule and thus could carry, and may produce specific antibody molecules. Such a conclusion supports the theory that the small lymphocyte may be the site of specific recognition of antigens in the primary response.