Developmentally regulated expression of survivin in the human thymus

Survivin is a member of the inhibitor-of-apoptosis (IAP) family. It has been reported to be expressed during development, but not in differentiated normal tissue. However, its expression has been reported to be high in the thymus. To assess the role of survivin in human thymocyte development, we investigated the expression of survivin using reverse-transcriptase-polymerase chain reaction, flow cytometry, and immunohistochemistry in freshly isolated human thymocytes. Survivin was expressed in all thymocyte subsets but its expression level was developmentally regulated. Its expression was low in the double negative (DN) thymocytes, upregulated in double positive (DP) thymocytes, and was highest in the T-cell receptor(high), late DP thymocytes; it was then downregulated in the single positive thymocytes and negative in the peripheral blood T cells. Moreover, there was a positive correlation between the expression of survivin and that of CD69 and Bcl-2 in DP thymocytes. These results suggest that survivin may play an important role in the T-cell development in the human thymus.