Immunological activity of fractions of thymus factor X (TFX).

Immunotropic activity of 5 fractions of thymus extract (TFX) was evaluated in vitro. It was shown that, except fraction IV, they exerted protective effect in relation to the cytotoxicity activity of hydrocortisone. Beside, all but fraction IV restored the ability of lymphocytes for rosette formation, suppressed previously by the introduction of imuran. In both experimental systems fraction V exhibited the strongest effect. The division of fraction V into subfractions--A and B showed that practically all thymosin activity is concentrated in subfraction B.