Incubation of human peripheral blood lymphocytes with Concanavalin A (Con A) in serum-free media results in the generation of soluble active substances which induce DNA synthesis in autologous and allogeneic lymphocytes (mitogenic factor – MF) and inhibit macrophage migration (migration inhibitory factor – MIF). Both substances retain their activity after removal of Con A by binding of Con A to highly polymerized dextrans. Using Sephadex column chromatography, MF and MIF show different elution profiles and can be completely separated from each other. The heterogeneity of MF and the similarity of MIF in molecular weight induced in Con A and PPD stimulated cultures is discussed.
In order to demonstrate mitogenic activity released by human lymphocytes, supernatants from “primary cultures” (sensitized cells together with antigen) were transferred to “secondary cultures” (autologous or homologous sensitized or non‐sensitized lymphocytes). It could be shown that sensitized human lymphocytes excrete a soluble mitogenic factor after exposure to antigen which induces DNA synthesis in secondary cultures. The production of this mitogenic factor was immunologically specific. Factor production could also be demonstrated in an autologous system; therefore the effect of mitogenic factor is independent of histocompatibility antigens. Maximal production of mitogenic activity was obtained after 24 h of primary culture. The amount of activity produced was dependent on the dose of antigen added. An effect of mitogenic factor on secondary cultures was already visible after 48–60 h; the maximal response, however, was seen after 120–136 h of incubation. The kinetics of DNA synthesis obtained were comparable to kinetics induced by specific antigen in short term lymphocyte cultures. DNA synthesis in secondary cultures was dependent on the amount of supernatant added. Since the addition of further antigen to different volumes of supernatants did not lead to an enhanced factor activity, the operation of mitogenic factor was not dependent on the amount of antigen present. Supernatants obtained after 3 days of primary culture, tested on autologous lymphocytes, exhibited a lower response in most instances when compared with the reconstituted controls. This effect may be due to an inhibitor produced by the cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.