[Effect of ionizing radiation on the thymus stroma of embryos and newborn mice]

The lobes of thymus of newborn mice irradiated on 17 day of embryonic life or on 1 day after the birth were transplanted under the renal capsule of adult mice. The recipients were thymectomized, lethally irradiated and reconstituted by syngeneic bone marrow cells treated by monoclonal anti-Thy-1-antibody and complement 1 month before the transplantation of thymus. Colonization of the thymus transplants, number and functional activity of T cells in peripheral lymphoid organs of recipients were measured 30 day after the transplantation of thymus. The colonization of the thymus transplants was decreased after irradiation of the thymus donors in doses of 6 and 8 Gy. The number of L3T4+ cells (T helpers) in the lymph nodes of the recipients and the level of the humoral immune response on thymus-dependent antigen were decreased after the exposure of the thymus donors to dose of 1 Gy or higher and the level of graft-versus-host reactivity of lymph node cells--after the dose of 2 Gy and higher. The degree of the suppression of the humoral immune response was higher when the donors of thymus were irradiated in embryonal period of development than after the birth. Thus the damage of the components of thymic microenvironment responsible for the T cell development can be arisen by relatively low doses of ionizing irradiation.