title: CD5 expression is developmentally regulated by T cell receptor (TCR) signals and TCR avidity.
abstract: Recent data indicate that the cell surface glycoprotein CD5 functions as a negative regulator of T cell receptor (TCR)-mediated signaling. In this study, we examined the regulation of CD5 surface expression during normal thymocyte ontogeny and in mice with developmental and/or signal transduction defects. The results demonstrate that low level expression of CD5 on CD4(-)CD8(-) (double negative, DN) thymocytes is independent of TCR gene rearrangement; however, induction of CD5 surface expression on DN thymocytes requires engagement of the pre-TCR and is dependent upon the activity of p56(lck). At the CD4(+)CD8(+) (double positive, DP) stage, intermediate CD5 levels are maintained by low affinity TCR-major histocompatibility complex (MHC) interactions, and CD5 surface expression is proportional to both the surface level and signaling capacity of the TCR. High-level expression of CD5 on DP and CD4(+) or CD8(+) (single positive, SP) thymocytes is induced by engagement of the alpha/beta-TCR by (positively or negatively) selecting ligands. Significantly, CD5 surface expression on mature SP thymocytes and T cells was found to directly parallel the avidity or signaling intensity of the positively selecting TCR-MHC-ligand interaction. Taken together, these observations suggest that the developmental regulation of CD5 in response to TCR signaling and TCR avidity represents a mechanism for fine tuning of the TCR signaling response.
authors.affiliation: Laboratory of Mammalian Genes and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: H S
authors.initials: HS
authors.lastname: Azzam
authors.forename: A
authors.initials: A
authors.lastname: Grinberg
authors.forename: K
authors.initials: K
authors.lastname: Lui
authors.forename: H
authors.initials: H
authors.lastname: Shen
authors.forename: E W
authors.initials: EW
authors.lastname: Shores
authors.forename: P E
authors.initials: PE
authors.lastname: Love
mesh_terms: D000818:Animals; D000906:Antibodies; D015703:Antigens, CD / Q000032:analysis / Q000276:immunology; D018956:CD5 Antigens / Q000276:immunology / Q000378:metabolism*; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D005260:Female; D005434:Flow Cytometry; D015329:Gene Rearrangement, T-Lymphocyte / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000378:metabolism; D016131:Lymphocyte Subsets / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000906:Antibodies; D015703:Antigens, CD; D018956:CD5 Antigens; D004268:DNA-Binding Proteins; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; C499308:Rag2 protein, mouse; D011948:Receptors, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta; C064655:V(D)J recombination activating protein 2; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)