![]() ![]() Nonetheless, diversity in the MHC genes can be maintained over long evolutionary time spans, resulting in balanced polymorphism, which in turn could explain the evolution of MHC “supertypes”. The high variability of the MHC genes is thought to be due to an evolutionary “arms race” between pathogens and the immune system which results in a dynamic process affecting frequencies of MHC alleles and pathogens. In contrast, bonobos exist in a single geographic range comparable in size to the range of a single chimpanzee subspecies and have limited genetic substructure. Chimpanzees are classified as four geographically delimited subspecies, which have differing population histories and average genetic heterozygosities. ![]() Despite the recent divergence of bonobos and chimpanzees, the latter species possesses an additional class I locus, termed A-like, which is not present in any other African ape species. Chimpanzees and bonobos are the closest evolutionary relatives of humans with an estimated most recent common ancestor between 1 and 2.6 mya (, reviewed in ). ![]() The classical MHC class I genes are defined in humans as HLA-A, - B and - C and orthologs are found in chimpanzees ( Pan troglodytes), bonobos ( Pan paniscus) and gorillas ( Gorilla gorilla and Gorilla beringei). In addition to their role in the adaptive immune system, MHC class I molecules are also involved in the innate immune system by interacting with the killer cell immunoglobulin-like receptors (KIR receptors) occurring on natural killer cells (NK cells) and controlling the NK cell response, which results in lysis of the infected cells. The interaction of MHC molecules with immunocompetent cells triggers an immune response. MHC molecules comprise two main classes: MHC class I molecules present peptides derived from intracellular pathogens while MHC class II molecules present peptides from the extracellular environment, including peptides from extracellular pathogens (reviewed in ). These genes underpin the mammalian adaptive immune system by coding for molecules presenting peptides to immunocompetent cells. The most diverse genes found in higher vertebrates constitute the major histocompatibility complex (MHC). However, special caution is needed to prevent introduction and spread of new viruses to bonobos, as their defensive ability to cope with new viruses could be limited compared to chimpanzees. The effects of this finding on the immune defense against viruses in wild living bonobos are unclear. Our results suggest a reduced MHC class I viral peptide binding ability at the B and C loci in bonobos compared to chimpanzees. Furthermore, we found evidence of a limited peptide binding repertoire in bonobos by tree-based visualization of functional clustering of MHC molecules, as well as an analysis of peptides bound by both species. We found a lower percentage of bound peptides in bonobos at the B locus in the “population”-level comparison and at the B and C loci in the “individual”-level comparison. We conducted multiple levels of analysis on the “species”-, “population”- and “individual”-level to account for the characterization of MHC variation in a larger number of chimpanzees and their broader geographic distribution. We examined the peptide binding ability of all 219 different MHC class I molecules to 5,788,712 peptides derived from 1432 different primate viruses and analyzed the percentage of bound peptides and the overlap of the peptide binding repertoires of the two species. Here, we use a bioinformatic approach to analyze the viral peptide binding ability of all published bonobo MHC class I molecules ( n = 58) in comparison to all published chimpanzee MHC class I molecules ( n = 161) for the class I loci A, B, C and A-like. Although several studies found reduced MHC class I diversity in bonobos in comparison to the closely related chimpanzee, it is unclear if this lower diversity also influences the functional ability of MHC class I molecules in bonobos. ![]() The highly polymorphic genes of the major histocompatibility complex (MHC) class I are involved in defense against viruses and other intracellular pathogens. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |