Influence of a radioprotector WR-638 on the lymphoid compartment of the irradiated rat thymus: a flow cytometric analysis.

The T cell composition of the thymus of X-ray irradiated (3.5 Gy) Wistar rat protected with WR-638 was analyzed by flow cytometry using monoclonal antibodies directed to the Thy 1.1, CD43, CD2, CD5, CD4, CD8 and class I and II MHC antigens. It was shown that this dose of X-rays caused cyclic changes in thymic cellularity manifested as: primary involution (until day 2), primary regeneration (from days 2 to 14), secondary involution (from days 14 to 21) and secondary regeneration (from days 21 to 30). WR-638 reduced the magnitude of thymocyte depletion in the primary involutive phase of the irradiated thymi, primarily as a result of protection of Thy 1.1high+ CD2low+ CD5high+ CD4+ CD8+ class I antigen high+ subpopulations of thymocytes. In the early regenerative phase, WR-638 accelerated the regeneration of CD4-CD8- and CD4-CD8+ thymocyte subsets, followed by subsequent increase of CD4+CD8+ and CD4+CD8- thymocyte subsets. Secondary involutive and regenerative phases in protected animals were characterized by higher absolute cell number of almost all thymocyte subpopulations in comparison with those in irradiated, non-protected animals.