The major histocompatibility complex and antigen presentation (chapter 8) summary. Mhc encodes class i, ii molecules functioning in antigen presentation to t cells, class iii molecules with diverse functions. Mhc genes tightly linked and generally inherited as a block from parents groups of alleles called haplotypes. Mhc genes are polymorphic many alleles exist for each genes polygenic many different genes exist with a single domain. Class ii molecules large glycoprotein chain and 2-microglobulin, protein. Class i molecules expressed on almost all nucleated cells. Class ii molecules restricted to b cells, macrophages & dendritic cells * apc. Proteasomes and transporters involved in antigen processing (before t cell recognition) Mhc alleles influence immune responsiveness and antigen presenting ability also susceptibility to many diseases. Class i molecules present endogenous antigen to cd8+ tc cells. Class ii molecules present exogenous antigen to cd4+ th cells. Endogenous antigens degraded into peptides within cytosol by proteasomes.