Thymus and bursa dependence of lymphocyte mitogenic factor in the chicken

AMONG the soluble products generated during activation of rodent or human lymphocytes 1 , lymphocyte-stimulating (‘mitogenic’) factors are detected by their ability to accelerate DNA metabolism of freshly cultured allogeneic or syngeneic lymphocytes 2–8 . If such lymphocyte activation products function as mediators of cellular immunity 1,9–11 , their activities will be generated independently of the antibody-forming system. In the chicken, antigen-stimulation of sensitized lymphocytes in vitro involves both thymus (T-) and bursa-(B-)-dependent cells 12–14 . If antigen-induced lymphocyte transformations are generally mediated by lymphocyte mitogenic factors, both T-cells and B-cells should produce lymphocyte mitogenic factors when stimulated by specific antigen. We have therefore determined whether antigen-stimulated chicken lymphocytes generate a lymphocyte mitogenic factor and whether this response is affected by neonatal thymectomy or bursectomy.