The paper presents results of the in vitro study of the immunomodulating effect of T-activin in 54 patients with active primary pulmonary tuberculosis, with the purpose of establishing criteria for initiating the therapy with this preparation. The most sensitive test for the determination of immunomodulating effect of T-activin in vitro appeared to be the reaction of active rosette forming (Ea-RFCs). The investigations performed showed that the preparation of the thymus gland can be recommended for use in those patients only, in whom there is striking or moderate decrease in the count of active RFCs. In the presence of their normal content T-activin may bring about depression of cellular immunity.
