IMMUNOLOGY

Detailed explanation-1: -IgA has the capacity to form dimers, in which two monomer units, each comprising two heavy chains and light chains, are arranged in an end-to-end configuration stabilized by disulphide bridges and incorporation of J (joining) chain.

Detailed explanation-2: -IgA antibody synthesized in the lamina propria is secreted as a dimeric IgA molecule associated with a single J chain (see Fig. 4.23).

Detailed explanation-3: -Whereas secretory IgA is dimeric, serum IgA is composed mainly of monomers. The monomeric form and the lack of the secretory component enable serum IgA to bind to Fc-receptor I (FcRI) expressed by myeloid cells, such as monocytes, neutrophils, and some subsets of macrophages and dendritic cells (DCs)3.