CD3{varepsilon}-mediated signals rescue the development of CD4+CD8+ thymocytes in RAG-2 / mice in the absence of TCR {beta} chain expression

Recent studies have shown that TCR ß chain expressioncan effect the differentiation of CD4^–CD8^– double-negative(DN) thymocytes to CD4⁺CD8⁺ double-positive (DP) thymocytes.The TCR ß chain is expressed on the surface of DPthymocytes in association with CD3, and chains, suggestinga potential role for CD3 components in this signaling process.We now report detection of a very tow level of surface expressionof CD3 on adult DN RAG-2^–/–; thymocytes. This surfaceCD3 was associated with CD3 and chains, as detected by anti-CD3immunoprecipitation analyses. Significantly, injection of anti-CD3mAb into RAG-2^–/– mice led to the accumulation ofan IL-2R^– CD2⁺ DP cell population and a nearly 100-foldincrease in thymic cellularity to essentially normal levels.Together, these data strongly indicate that TCR ßchain-mediated developmental signals are transduced by CD3 componentsand provide potential insights into mechanisms by which TCRß chain expression may effect this process.