Human TCR/CD3 is a complex structure on the lymphocyte surface. It consists of the TCR alpha beta or TCR gamma delta heterodimer and the associated CD3 complex. The CD3 complex is composed of six polypeptides with usually four different transmembrane CD3 chains, gamma, delta, epsilon. and zeta. Three different dimers, gamma epsilon, delta epsilon, and zeta zeta, constitute the CD3 complex. The MW of CD3epsilon is 20 000 (Campana, 1987). CD3 is first detectable in early thymocytes and its appearance probably represents one of the earliest signs of commitment to the T cell lineage. In cortical thymocytes, during early stages of maturation, the CD3 antigen is predominantly present in the cell cytoplasm. In medullary thymocyles, the CD3 antigen is predominantly detected on the cell surface (Swerdlow, 1988; Beverley, 1981). The majority of T cell neoplasms also expresses CD3, but it is absent from non-T-cell lymphoid malignancies (McMichael, 1987). Consistent with the pattern of synthesis of the antigen in normal thymocytes, the earliest site detectable within neoplastic cells is the cell cytoplasm (Swerdlow, 1988).，官网链接：https://www.sigmaaldrich.cn/product/mm/fcmab168p 默克 科研、开发、生产。 作为生命科学行业的全球领先供应商，我们致力于为科研、生物技术开发和生产，以及制药药物疗法开发和生产提供各类解决方案和服务。

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