TCR gamma/delta+ dendritic epidermal T cells as constituents of skin-associated lymphoid tissue.
The epidermis of all strains of normal mice is populated by two distinct dendritic, bone marrow-derived cells: Langerhans cells and CD4-CD8- Thy-1+ dendritic epidermal T cells (DETC). The overwhelming majority of DETC are an unusually homogeneous population of thymic-dependent cells which express CD3-associated T-cell antigen receptors (TCRs) of the gamma/delta type, thereby distinguishing them from conventional CD4+CD8- or CD4-CD8+ T cells expressing CD3-associated alpha/beta TCR. Most DETC are ontogenetically primitive, derived from early fetal thymocytes with a preferential, but poorly understood tropism for the epidermis. Like the TCR on other populations of gamma/delta cells, which preferentially populate other epithelia such as in the gut and lung, the TCR on most DETC selectively utilize particular variable (V) gene segments (i.e., V gamma 3 and V delta 1 for DETC vs V gamma 5 and V delta 4 or V delta 6 for intestinal intraepithelial lymphocytes). However, unlike other gamma/delta populations whose TCR junctional regions exhibit marked heterogeneity, DETC junctional diversity is extremely limited. This lack of TCR heterogeneity among DETC suggests they recognize a narrow range of physiologic ligands (antigens) and that this recognition is restricted not by conventional polymorphic class-I or class-II MHC molecules, but rather by relatively nonpolymorphic self MHC-like molecules of the class Ib MHC type [e.g., Qa, TL, and CD1 (T6)]. Additional studies are required to clarify precisely what DETC recognize, their relevant biological functions, as well as their relationship(s) to the gamma/delta cells recently identified in human skin.
Tigelaar
R E
RE
Department of Dermatology, University of Texas, Southwestern Medical Center, Dallas.
Lewis
J M
JM
Bergstresser
P R
PR
D000818:Animals; D000941:Antigens / Q000276:immunology; D015703:Antigens, CD / Q000032:analysis; D000954:Antigens, Surface / Q000032:analysis; D003713:Dendritic Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D000078404:Epidermal Cells; D004817:Epidermis / Q000276:immunology / Q000378:metabolism; D006801:Humans; D008221:Lymphoid Tissue / Q000166:cytology* / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism*; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta; D012867:Skin / Q000166:cytology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology; D018800:Thy-1 Antigens; D013950:Thymus Gland / Q000166:cytology / Q000196:embryology
D000941:Antigens; D015703:Antigens, CD; D000954:Antigens, Surface; D011948:Receptors, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta; D018800:Thy-1 Antigens