Background: The aim of the study is the investigation of the factors of innate immunity and formation of specific immune reactions in rats (antibody forming and formation of delayed hyperresponsivene reactions) after Propes (an extract of a bovine fetus liver) usage. Material and methods: In the study we used CBA mice and white rats. Propes was used in dose 90 mg/kg subcutaneously for 10 days. On the 5th day after immunization by sheep erythrocytes in spleen of animals were evaluated antibody-forming cells using Jerne-Nordin technic, was haemagglutinin content, studied using simple haemagglutination technic in serum. Hyperresponsivene reactions were carried out using E. V. Gulling and М. B. Sambur method. Results: It was found out that Propes doesn’t exert an activity of factors innate immunity, doesn’t decrease natural cell-mediated cytotoxicity against metabolically low-level target cells. Propes exerts immunomodulating activity towards regulatory and effector cells of immune system, increases T-killers/ helpers in mouse spleen, increases activity of NK-cells in mouse spleen and human blood. The drug suppresses primary humoral immune response on xenograft erythrocytes and immune hyperresponsiveness reactions. It has the influence on high proliferating systems and has immunomodulating properties, which depends on the time of administration and dosage regimen. Conclusions: Immunomodulatory properties of Propes have ability to change the level of antigen differentiation of lymphoid organs and blood cells of experimental animals and humans, especially towards proliferative processes, regulates humoral and cell immune response. It doesn’t exert the negative influence on cellular factors of innate immune response.