Purification and Characterization of Human Serum and Secretory IgA1 and IgA2 Using Jacalin

Human immunoglobulin A (IgA) is found in serum and secretions in several different forms (1), Serum IgA is produced by the bone marrow and is pre-dominately monomeric (M ( r )= 160 kDa). Most of the IgA in secretions (sIgA) is polymeric, predominantly dimeric, comprising two monomer subunits linked together by intersubunit disulfide bonds and a cysteine-rich polypeptide termed J-chain (M ( r )= 16 kDa). Polymeric IgA in secretions, but not in serum, contains an additional heavily glycosylated protein called secretory component (SC) (M ( r )= 70 kDa).