The major histocompatibility complex (mhc) is a set of proteins expressed on the surface of antigen presenting cells that recognize and bind to pieces of antigens so that they can be presented to the appropriate t cell. not only is the expression of these proteins controlled by more than one gene (polygenic), but individuals with different alleles for mhc proteins are heterozygous for that gene. what advantage does the mhc proteins being polygenic and codominant offer to the individual? a) there will be a lower level of immune rejection for this individual should they receive a blood or organ transplant. b) there will be an increased resistance to hiv infection, as the t cells will be less likely to be invaded by the virus. c) there is a larger variety of mhc proteins that can be expressed on the cell surfaces of their immune cells, providing a wider opportunity to recognize and attack pathogens. d) there is an increased opportunity for anaphylaxis, as presenting a wider variety of mhc proteins on the cell surfaces of immune cells will result in a body-wide response to antigens.