부산대학교 도서관

The major histocompatibility complex (MHC) class I-related molecules A and B (MICA and MICB) are stress-inducible cell surface antigens that are recognized by immunocytes bearing the receptor NKG2D. In our study we estimated the average number of synonymous (πs ) and nonsynonymous nucleotide substitutions (πa ) per site in exons 2–4 of MICA and MICB. In exons 2 and 3 of MICB only nonsynonymous substitutions were found, and in exon 3 of MICA πa clearly exceeded πs. This finding is in contrast to the evolutionary parameters found in most other genes, and is reminiscent of the elevated πa values caused by overdominant selection in the peptide-binding region of conventional MHC class I molecules. It may be explained by the hypothetical interaction with nonpeptide antigens, or by resistance against pathogens. [ABSTRACT FROM AUTHOR]