Concanavalin A as an Inducer of Human Lymphocyte Mitogenic Factor

IT is likely that pharmacological products of antigen : lymphocyte interaction (“lymphokines”) act as mediators and regulators of a variety of cellular immune responses^1,2. This view is strengthened by demonstrations that phytomitogen lectins induce lymphocytes to generate products with similar biological activities^3,4 and physicochemical characteristics⁵, to the lymphokines. Increasing evidence suggests that mitogenic lymphokines may mediate lymphocyte transformation responses in vitro and facilitate lymphoid cell cooperation in vivo (refs. 1,2,6–9). The study of mitogenic factor production by phytomitogens which may predominantly activate thymus-dependent lymphocytes (Concanavalin A (ConA))^8,9 provides a model approach to the investigation of lymphokine function in man. Powles et al.⁴ have described a ConA-induced mitogenic factor which stimulated autologous human lymphocytes only, whereas antigen-induced lymphocyte factors generally stimulate both allogeneic and syngeneic lymphocytes^11–13. Interest in ConA as an inducer of human lymphocyte mitogenic factors would be widened if conditions were found in which ConA stimulated human lymphocytes to generate products which were mitogenic for both allogeneic and autologous lymphocytes. As a lymphokine stimulant, ConA has the advantage that it is largely removed from culture fluids by absorption to cross-linked dextrans (‘Sephadex G-50’) or serum glycoproteins¹⁴. Here we demonstrate that a ‘Sephadex’-binding fraction of ConA (ConA- V) induces human lymphocytes to generate a mitogenic factor which activates both allogeneic and autologous lymphocytes.