In Humans, IgA Is Produced in Copious Amounts, Estimated to Be

In humans, IgA is produced in copious amounts, estimated to be a rate of 3 g/day. Nearly all of the IgA secreting plasma cells are found in the gastrointestinal (GI) tract where the secreted IgA is transported across the GI epithelium into the lumen of the gut. There, this antibody protects the GI epithelium against intestinal pathogens. In contrast, none of the GI resident long-lived antibody secreting cells produce antibodies of the IgG class. The differential localization of long-lived antibody secreting cells producing IgA compared to those producing IgG is likely due to:

A) Their interactions with T_FH cells specific for pathogens that infect the gut
B) The lack of germinal centers in the mucosal lymphoid organs
C) The absence of S1PR1 expression on IgA-secreting plasma cells
D) Their priming and differentiation in mucosal lymphoid organs
E) Their inability to access the bone marrow compartment