The MHC is thought to be the most dense region of genes and most polymorphic region of genes in the human genome. It is highly unlikely that your MHC genes match any of your friends!! Tissue matching in this gene region is important in transplantation medicine and that is why this gene complex was originally called the histocompatibility complex. However, of all the millions of different allele combinations which could occur, each individual only expresses a small subset of all the alleles. Because the MHC presents antigens to the immune system, this means that we all "see" antigens slightly differently from one another and it is why we are more or less susceptible to some diseases and syndromes compared to others.
According to the published literature this is a conundrum for evolution or any origin model of the MHC. Consider this statement in a recent publication:
"An adaptive immune response is usually initiated only if a major histocompatibility complex (MHC) molecule presents pathogen-derived peptides to T-cells. Every MHC molecule can present only peptides that match its peptide-binding groove. Thus, it seems advantageous for an individual to express many different MHC molecules to be able to resist many different pathogens. However, although MHC genes are the most polymorphic genes of vertebrates, each individual has only a very small subset of the diversity at the population level. This is an evolutionary paradox."
Since we have also been exploring teleological explanations for the immune system, what might a teleogical view be regarding the MHC? What design advantage does the MHC provide?
Please share your thoughts with the group in this blog.
DUE Dec 10
