IgA antibodies are synthesized in plasma cells  underneath epithelial basement membranes of the respiratory epithelia, the gut, tear and salivary glands, and the lactating gland. The IgA dimer diffuses across the basement membrane while the poly-Ig receptors binds to the epithelial cell. The complex undergoes transcytosis and then is transported in a vesicle through the cell. The poly-Ig receptor then leaves the IgA-binding component (as the secretory component). The rest of the poly-Ig receptor is degraded, and IgA is then transported across the epithelia.

Transcytosis of IgA antibody and its mediation by the poly-Ig receptor

- Major effector functions of each isotype are dark red
- lesser functions = dark pink
- minor function = light pink

University of Illinois at Chicago

IgG is the main isotype in the extracellular fluid and blood. It opsonizes pathogens for consumption by phagocytes and activates the complement system. IgG antibodies that are high-affinity are able to neutralize bacterial toxins (they bind to the receptor-binding site on the toxin molecule that stops the toxin from binding to the cell. Since these antibodies are able to scatter into tissue and entangle the toxins quickly, they are considered to be the principal neutralizing antibodies.

IgG antibodies and their functions/distributions

Janeway, C. A., & Jr. (1970, January 1). The distribution and functions of immunoglobulin isotypes. Immunobiology: The Immune System in Health and Disease. 5th edition. https://www.ncbi.nlm.nih.gov/books/NBK27162/#:~:text=IgG%20antibodies%20are%20usually%20of,and%20activate%20the%20complement%20system. 

Learn Before

Related

Learn After