TAPBP and infectious disease: Many features of the chicken MHC differ markedly from typical mammals (Figure 1), including the strong genetic associations with infectious disease mentioned above, the class III region on the outside of the class I and class II regions, the polymorphic TAP genes in between the two class I genes, a polymorphic tapasin (also called TAP binding protein, or TAPBP) gene nearby, the lack of an obvious tapasin binding site in TAP1, a polymorphic NK receptor/monomorphic ligand gene pair and a very low level of recombination across the region (20, 29).