The reparation-regeneration effects of the actoprotector etomerzol and the immunomodulant thymogen can be mediated by certain units of the immune system, in particular, by thymus. Both thymogen and etomerzol loss the hepatoprotector activity on the background of thymectomy, but still produce an immunomodulant effect by stimulating the production of antibody-forming cells in the spleen in response to changes in the immune system induced by various stressor factors (thymectomy, hepatectomy, or their combination). This property of etomerzol, together with the absence of influence upon the immune state of intact experimental animals, is evidence of a dominating immunomodulant activity of this drug.