IRAQI JOURNAL OF MEDICAL SCIENCES

Vitamin D, an evolutionarily conserved molecule essential for diverse life forms ranging from phytoplankton to mammals, plays a critical role in health beyond its classical functions. It promotes osteoclast differentiation indirectly via receptor activator of nuclear factor κB (RANKL) upregulation, facilitating intestinal calcium absorption, promoting renal calcium reabsorption, and stimulating the mineralization of the bone collagen matrix, thereby regulating calcium and bone homeostasis. Significantly, immune cells, including B lymphocytes, T lymphocytes, and antigen presenting cells express the vitamin D receptor (VDR) and possess the enzymatic to activate vitamin D. This locally produced vitamin D exert autocrine and paracrine immunomodulatory effects. Adequate vitamin D status influences both innate and adaptive immune responses, while deficiency is epidemiologically associated with increased susceptibility to infection and heightened risk of autoimmunity. Consequently, the immunomodulatory benefits of vitamin D supplementation in deficient individuals with autoimmune diseases extend beyond the regulation of calcium and bone metabolism.
Keywords Vitamin D, immune system, bone health, calcium absorption, autoimmunity
Citation Al-Taei OMS. Immunomodulatory effects of vitamin D: Bridging cellular defense and inflammatory control. Iraqi J Med Sci. 2026; 24(1): 1-9. doi: 10.22578/IJMS.24.1.1