Figure 1

Human IgA1 and IgA2 molecules as monomers, dimers (dIgA1 and dIgA2, respectively) and as secretory forms (SIgA1 and SIgA2, respectively). Green, heavy chain; yellow, light chain; red, J chain; blue, secretory component (SC); orange, O-linked oligosaccharides in the IgA1 hinge region. N-linked oligosaccharides are shown at the approximate locations in both IgA1 and IgA2 molecules.