Role of CD3 delta in T cell development

The T cell receptor (TCR)/CD3 complex consists of a TCRalphabeta heterodimer and invariant CD3gamma, delta, epsilon and zeta chains. CD3 components play a critical role in T-cell development and function. Thymocyte development is impaired at the CD4-CD8- double negative stage in CD3gamma-, epsilon-, or zeta-deficient mice, whereas CD3delta deficiency impairs thymocyte maturation at the CD4+CD8 +double positive stage. However, the stoichiometry of CD3gamma and CD3delta chains on the surface TCR/CD3 complex has not been determined. In the present study, transgenic mice expressing a truncated form of CD3delta and CD3gamma that lacked the whole cytoplasmic domain were employed to show that the surface TCR/CD3 complex contains one molecule each of CD3delta and CD3gamma. During our studies, we found that the human CD3delta/epsilon transgene could rescue thymocyte development not only in CD3epsilon -/- mice, but also in CD3gamma-/- mice. Our data suggested that CD3delta may be required for the preTCR function in human, but not in mice