Isolation of substances that stimulate RNA synthesis from red kidney bean: their activities in lymphocytes and Escherichia coli

Interaction of ascorbate with the radioprotective effect of mercaptoethylamin. An exploratory study in mice, whole animals and cell cultures

The injection of ascrobate together with cysteamine (beta-mercaptoethylamin or MEA) was shown to cause a partial reversion of the radioprotective action of MEA in mice, and simultaneously of the suppressive action of MEA on RNA synthesis in bone marrow cells. In mouse spleen lymphocytes stimulated by concanavalin A in vitro, MEA and ascorbate exhibited a strong antagonism, neutralizing each other's inhibitory action on RNA synthesis. The latter effect failed to appear after chelation of trace metals, and it is indicated that the ability of ascorbate to counteract the effects of MEA on radiosensitivity and metabolism requires the formation of oxidized products, probably monodehydroascorbate, in agreement with previous observations on bacteria.

Inhibition of in vitro immune responses by a fraction from seminal plasma

We studied the inhibitory effect of a fraction of bovine seminal plasma on in vitro lymphocyte responses to specific and nonspecific ligands. Seminal plasma was fractionated by Sephadex G-100 chromatography, and the inhibitory component was found to have a molecular weight of above 100,000 daltons. This fraction was devoid of lymphocytotoxicity and could inhibit, in a dose-dependent mode, both the primary antibody response of normal mouse spleen cells to the thymus-dependent antigen sheep erythrocytes and the one-way mixed lymphocyte reactions. Concanavalin A-induced proliferative T-cell responses were also inhibited by the same fraction. The inhibition of the T-lymphocyte responses to Con A was complete at suboptimal concentrations of the mitogen and could only partially be overcome at supraoptimal concentrations. Four other fractions in seminal plasma were also studied in this particular system, three being without effect and one being stimulatory. The inhibitory fraction was also found to inhibit the polyclonal B-cell responses induced by fetal calf serum. The importance of the present findings for the immunophysiology of reproduction are discussed.