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 histocompatibility complex (MHC) class I alleles, Mamu‐A*05 and Mamu‐A*07 . This resulted in an intron 2 that was nearly twice the length of any other intron 2 of primate MHC class I genes sequenced to date. This insertion was most 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 this insertion in two rhesus MHC class I genes is surprising given the uniformity in length and sequence of introns of functional HLA‐A, ‐B and ‐C genes.