[Biological activity of thymus preparations from sheep of various ages].

Thymus active fractions from 3-year-old sheep were shown to cause immune response stimulation to sheep red blood cells in experimental immune deficiency in mice. The fraction from fetal lamb and sheep thymus was more active than that of mature animals in increasing immune rosette-formation in the lymph of central and peripheral organs of the immune deficient mice. All the preparations recovered the number of splenocytes in immune deficient mice. Therefore, thymus active fractions obtained from sheep at different stages of ontogenesis had a stimulating effect on cell proliferation and immunogenesis.