An unusual insertion in intron 2 of apparently functional MHC class I alleles in rhesus macaques

Here we describe a nucleotide insertion in intron 2 of two rhesus major his tocompatibility complex (MHC) class I alleles, Mamu-A*05 and Mamu-A*07. Thi s resulted in an intron 2 that was nearly twice the length of any other int ron 2 of primate MHC class I genes sequenced to date. This insertion was mo st similar (93% identity) to the beginning of intron 3 of HLA-A alleles. It was also similar to intron 3 of several human MHC class I pseudogenes and MHC class I pseduogenes from cotton top tamarin and cat. The finding of thi s insertion in two rhesus MHC class I genes is surprising given the uniform ity in length and sequence of introns of functional HLA-A, -B and -C genes.