Organization of the human CD3 locus on chromosome 11.

Three CD3 genes, gamma, delta, epsilon, map to human chromosome 11 band q23. A 75-kb region of 11q23 containing all three genes has been characterized by field inversion gel electrophoresis and molecular cloning. The CD3 genes lie within a stretch of 50 kb of DNA, orientated 3'-CD3 gamma-5': 5'-CD3 delta-3': 3'-CD3 epsilon-5'. Only 1.6 kb separate the CD3 gamma and CD3 delta genes, while the CD3 delta and CD3 epsilon genes are approximately 22 kb apart. CD3 gene expression is one of the first events during the maturation of the thymocyte, and therefore the clustering of CD3 genes may define a chromatin domain which is activated early in T cell development.