Purpose of review: Significant advances have been made in the characterization of Vitamin D and the Vitamin D receptor (VDR) in immune function. The studies of signaling pathways involved in the response to infection and inflammation have led to a more detailed understanding of the cellular response to Vitamin D through VDR. This review summarizes recent progress in understanding how Vitamin D contributes to mucosal immune function, particularly in relation to the molecular mechanisms by which Vitamin D and VDR influence mucosal immunity, bacterial infection, and inflammation.
Recent findings: Recently, it was shown that Vitamin D modulates the T cell antigen receptor, further demonstrating that Vitamin D has a nonclassical role in immunoregulation. The anti-inflammation and anti-infection functions for Vitamin D are newly identified and highly significant activities. Vitamin D/VDR have multiple critical functions in regulating the response to intestinal homeostasis, tight junctions, pathogen invasion, commensal bacterial colonization, antimicrobe peptide secretion, and mucosal defense. Interestingly, microorganisms modulate the VDR signaling pathway.
Summary: Vitamin D is known as a key player in calcium homeostasis and electrolyte and blood pressure regulation. Recently, important progress has been made in understanding how the noncanonical activities of Vitamin D influence the pathogenesis and prevention of human disease. Vitamin D and VDR are directly involved in T cell antigen receptor signaling. The involvement of Vitamin D/VDR in anti-inflammation and anti-infection represents a newly identified and highly significant activity for VDR. Studies have indicated that the dysregulation of VDR may lead to exaggerated inflammatory responses, raising the possibility that defects in Vitamin D and VDR signaling transduction may be linked to bacterial infection and chronic inflammation. Further characterization of Vitamin D/VDR will help elucidate the pathogenesis of various human diseases and in the design of new approaches for prevention and treatment.