Molecular Typing of the MHC Class I Chain-Related Gene Locus

The human major histocompatibility complex (MHC) class I chain-related genes A and B (MICA and MICB ) are located within the human leukocyte antigen (HLA) class I region of chromosome 6 (1 ). Their organization, expression, and products differ considerably from classical HLA class I genes (2 ). MIC proteins are considered to be markers of “stress” in the epithelia (3 ), and they act as ligands for cells expressing a common activatory natural killer cell receptor (NKG2D) (4 ). MIC proteins are also highly polymorphic (5 ), although the functional implications of this polymorphism remain unclear (6 ).