Chromosomal mapping of the second human CD8B gene locus

• Published in: Immunogenetics (New York) 1996-01, Vol.43 (4), p.220-226
• Main Authors: Zhang, X L, Heng, H H, Yang, Y, Tsui, L C, Parnes, J R, Chamberlain, J W
• Format: Article
• Language: English
• Subjects: Bacteriophage P1 - genetics; CD8 Antigens - genetics; Chromosome Mapping; Chromosomes, Human, Pair 2; Cloning, Molecular; Humans; In Situ Hybridization, Fluorescence; Multigene Family; Restriction Mapping
• ISSN: 0093-7711; 1432-1211
• DOI: 10.1007/s002510050049

The alpha beta T-cell receptor (TCR) expressed by most T lymphocytes recognizes foreign antigen (Ag) associated with class I or class II proteins encoded by the major histocompatibility complex (MHC). CD8 and CD4 are molecules expressed by distinct subsets of T cells and are referred to as T-cell co-receptors because they aid the TCR in these recognition events. The mutually exclusive pattern of expression of these co-receptors distinguishes the two sublineages of alpha beta TCR T cells: CD8 super(+)CD4 super(-)/cytotoxic T cells which recognize Ag bound to class I MHC, and CD8 super(-)CD4 super(+)/helper T cells which recognize Ag bound to class II MHC. CD8 (usually expressed as a heterodimer of CD8 alpha and CD8 beta chains) and CD4 undergo a complex pattern of regulated expression during T-cell maturation. In the thymus, the most immature cells progress from expressing neither CD8 nor CD4 (the double-negative/DN stage) to an intermediate stage at which both are co-expressed (the double-positive/DP stage). As a result of thymic selection and further differentiation, DP cells give rise to the most mature thymic cells, and finally, to peripheral T cells which are either MHC class I-restricted CD8 super(+)CD4 super(-) CTL or MHC class II-restricted CD8 super(-)CD4 super(+) helpers. As part of our studies aimed at identifying the cis- and trans-active regulatory mechanisms which control expression of CD8 during thymic development, we previously described the isolation of P1 bacteriophage DNA clones containing large segments of the human and mouse CD8 gene loci (Zhang et al. 1994). Detailed characterization of one mouse and one human CD8A clone showed that they contained inserts of about 85-90 kilobases (kb) which were faithful replicas of the endogenous chromosomal loci (Zhang et al. 1994). In the mouse there is a single gene for CD8 alpha (CD8A) and a single gene for CD8 beta (CD8B) which are separated by about 36 kb and located at region 2 on chromosome 6 (Parnes 1989). The mouse P1 CD8A clone was shown to map to this position.