Organization and expression of genes encoding iga heavy chain, polymeric ig receptor, and j chain

This chapter discusses the structure and expression of the genes encoding IgA heavy chains, polymeric Ig receptors, and J chains. The chapter also compares and contrasts the IgA genes of various species. A secretory immune system is present in most of the mammals, including primitive mammals such as insectivores, monotremes, and marsupials. Genes encoding IgA heavy chains have been cloned from several mammals including-man, mouse, rat, rabbit, pig, horse, and cattle. These cloned Cα genes are highly similar to each other and can be used as probes to clone Cα genes of other mammals. In contrast to mammalian Cα genes, which encode three domains, the chicken Cα gene encodes a heavy chain with four domains. Most mammalian species have one or two IgA isotypes expressed in secretions, but rabbits have at least 11 IgA isotypes. Genes encoding pIgR are cloned from rabbit, human, mouse, cattle, rat, and possum, whereas J chain genes have been cloned from mouse, human, cattle, chicken, possum, bullfrog, clawed toad, turtle, shark, and earthworm.