Publisher Summary This chapter discusses the impact of new information concerning IgA
physiology on the immune system. IgA should not be considered only as an isotype
providing specific humoral protection of mucosal surfaces but as an integral component of
the entire immune system. An unusual structural feature of human IgA is the heterogeneity of
the molecular forms with characteristic distribution in various body fluids. Though most IgA in
serum displays a typical four-polypeptide chain structure of the basic molecule with two Q …