A single amino acid substitution causes loss of expression of a MICA allele

The human major histocompatibility complex ((MHC) class I homologues MICA a nd MICE are stress-inducible surface molecules that are not associated with beta(2)-microglobulin and peptides, are expressed in intestinal epithelium and epithelial tumors, and are recognized by V(delta)1 gamma delta T cells , a subset of gamma delta T cells that is enriched in epithelial sites (Bah ram et al. 1994; Groh et al. 1996, 1998, 1999). Analogous to the interactio ns of MHC class I molecules with inhibitory or activating natural killer (N K) cell receptors that are expressed on NK cells and T cells (Lanier 1998, MICA/B are ligands for an activating receptor, NKG2D, which is expressed on most NK cells, CD8(+) alpha beta T cells and gamma delta T cells (Bauer et al. 1999).