The immunobiology of T cells with invariant gamma delta antigen receptors.

T cells bearing specific gamma delta TCR are the major lymphoid population in certain epithelial tissues. There are striking differences between these and peripheral T cells. The epithelial gamma delta 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 gamma delta 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 gamma delta T cells to perform specialized functions which differ from those of circulating alpha beta and gamma delta TCR+ cells. This review provides a summary of the characterization of gamma delta T cells found in epithelial tissues and speculates on the in vivo role of these cells.