Interplay of Immunity and Vitamin D: Interactions and Implications with Current IBD Therapy

Crohn's disease (CD) and ulcerative colitis (UC) are classified under inflammatory bowel disease (IBD) which has been linked to a multifaceted etiology involving both environmental and genetic factors that intersect with the vitamin D pathway. Dysfunctions in innate immune defense mechanisms in the epithelial compartment of the intestine play a crucial role in the pathogenesis of IBD. Symptoms of IBD are caused by excessive immune responses to luminal bacteria, and vitamin D has been shown to play a role in intestinal defense by aiding in the suppression of microbial invasion into the epithelium. Vitamin D, as an immunomodulator, can modify the innate immune response of the body. Vitamin D attenuates the transcription of pro-inflammatory cytokines that are upregulated in the event of epithelial stress common in patients with IBD. Vitamin D deficiency was identified in 82% of IBD patients compared to the 31% national average and has been linked to defective epithelial processes at both genomic and proteomic levels. Mucosal damage and an impaired immune response are at the center of IBD, and vitamin D aids in sustaining the structural integrity of epithelial cells while enhancing innate immune responses in the mucosa. Here we provide a systematic review of the pathophysiological effects of cytokines in IBD in the presence of vitamin D deficiency. Also, analysis of the immunomodulatory effect of vitamin D in regulating immunopathogenic factors like chemokines, growth factors, and human defensins will enhance knowledge of the underlying molecular mechanisms of the therapeutic role of vitamin D in IBD and thus aid in the development of better patient management strategies.