Fig 1.
How humoral immunity may promote gut homeostasis through regulation of BA biochemistry in the gut.
(A) Enterohepatic circulation of BAs under steady-state conditions. The vast majority of BAs are reabsorbed in the ileum for recirculation back to the liver. The remaining BAs (approximately 5% of the total pool) pass to the colon where bacterial metabolism leads to formation of secondary BAs. (B) In mucosal antibody deficiency, bacterial overgrowth in SI may result in aberrant bacterial BA metabolism that promotes SI enteropathy. Altered BA pools may be directly cytotoxic to ileal enterocytes (C), and/or may be less absorbable leading to chronic inflammatory responses in the gut that promote degradation of the ileal lining (D). Figure generated using Biorender.