the identification of a gene conversion event involving one of these allelic variable regions implicates conversion as a mechanism that acts on class ii beta genes to create sequence diversity in regions of ia molecules that interact with foreign antigen or a t cell receptor , regions where protein sequence polymorphism would presumably be selected for by the expanded ability it affords the organism to mount effective immune responses against a wider variety of foreign antigens .
C0301872
immune responses
C0003320
antigens