Thymus and Bursa Dependence of Lymphocyte Mitogenic Factor in the Chicken

AMONG the soluble products generated during activation of rodent or human lymphocytes¹, 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.