[Receptors for the secretory component on human thymic lymphocytes. Stimulation of their expression as affected by adenosine, theophylline and a thymic lymphocyte supernatant].

It has been established by indirect immunofluorescence that thymic lymphocytes bear receptors for secretory component (Rsc). The bound secretory component, i. e., in the molecule of secretory IgA, was found to react with a greater number of thymocytes than free secretory component. Such difference may indicate that T-Rsc have higher affinity to the bound secretory component than to free secretory component. However, this needs detailed investigation. The ability of thymocytes to express Rsc depends on the cellular cAMP level, as the treatment with adenosine and theophylline increases the number of cells with Rsc. Supernatant of a 3-hour thymocyte culture was also capable of stimulating the expression of Rsc. It is assumed that secretory component contained in great amounts in the thymus membrane system takes part in the differentiation of T alpha and Tsc cells of the thymus, which repopulate lymphoid organs and regulate their immune reactions. Rsc may also be useful in assessing the state of Tsc subpopulation in different pathological conditions.