[Effect of long-term administration of T-activin on the structure of the thymus]

Morphometry was used to study the effect of T-activin on the morphology of the thymus of (CBA X C57BL) F1 mice given 10, 15 and 20 injections of T-activin (1.0 micrograms i.p.). T-activin did not cause any pathological alterations in the thymus. Ten injections of T-activin activated the proliferation and migration of thymocytes from the thymus. Fifteen injections of T-activin eventuated in an increased surge of thymocyte migration from the thymus, whereas 20 injections gave rise to a new surge of proliferation and preparation or beginning of thymocyte migration from the thymus. It is concluded that prolonged injection of T-activin does not disturb the fluctuation pattern of thymus functioning but activates the transformation and migration of thymocytes.