RESUMO
Pronounced antitumor effect of Thymalin in doses lower than the therapeutic doses was shown in experiments on albino outbred male rats with transplanted sarcoma 45. Tumor growth arrest and its regression were observed in more than half of animals and in other cases, the growth was suppressed by 78%. Microstructural changes in the thymus were analyzed. Significant increase in lymphoproliferative activity and the content of tissue basophils and plasmocytes in the thymus lobules was observed. Tumor regression was accompanied by the development of stable antistress adaptation reactions of calm and elevated activation. High efficiency of Thymalin can be attributed to the use of lower doses of the substance and their modulation during the treatment course in accordance with the regimes of activation therapy.