Fig. 1.

Schematic representation of IgA formats, a monomeric IgA, b dimeric IgA, c secretory IgA. The monomeric IgA (mIgA) is formed by the paired heavy and light chains. The respective domains have been labeled, namely variable domains of the heavy (VH) and light (VL) chains, and constant domains of the heavy (Cα1, Cα2 or Cα3) and light (CL) chains. The joining chain (J chain) facilitates the dimerization of two mIgAs into a dimeric IgA (dIgA); the association of the dIgA with the secretory component results in a secretory IgA (SIgA)