The immunobiology of T cells with invariant γδ antigen receptors

T cells bearing specific γδ TCR are the major lymphoid population in certain epithelial tissues. There are striking differences between these and peripheral T cells. The epithelial γδ T cells exhibit highly restricted V gene use, preferential pairing of TCR chains, and lack of diversity at the junctions creating populations of cells with virtually identical TCR in particular epithelia. Generation of certain epithelial γδ populations appears to be restricted to a discrete stage early in development. The restricted localization and expression of invariant antigen receptors may equip the epithelial γδ T cells to perform specialized functions which differ from those of circulating αβ and γδ TCR⁺ cells. This review provides a summary of the characterization of γδ T cells found in epithelial tissues and speculates on the in vivo role of these cells.