October 2019 | Volume 6 | Issue 5 | Page 115 Hosts and Viruses Abstract | Vitamin D secosteroids are group of liposoluble prohormones consisting of fve diferent vitamins, the most important forms being vitamin D2 and vitamin D3. Previous and current studies revealed the putative immunomodulatory role of 1,25(OH) 2 D 3 besides its classical role of maintaining phosphorus and calcium metabolism inside body. Vitamin D is involved in homeostasis of innate and adaptive immune responses by modulating activity of monocytes, dendritic cells, macrophages and activation of T and B lymphocytes. Vitamin D modulates cytokine response and anti-microbial peptides (AMPs) production which boost innate immune response. Hypovitaminosis D is a signifcant risk factor for infectious and non-infectious diseases however its exact mechanism is still unknown, but low levels of vitamin D has been detected in diferent diseased cases. Recent investigations have reported various cells of body exhibiting vitamin D receptors and CYP27B1 which is capable of converting inactive form vitamin D into biologically active form 1,25(OH) 2 D 3 , that important for maintaining immune homeostasis. Tese fndings lead to more studies on the non-classical efects of vitamin D especially on immune responses. Vitamin D receptor (VDR) regulated transcription depends on co-modulators, which act in a cell specifc manner. Also, increasing the resistance to currently used antibiotics requires cost efective alternatives while vitamin D can serve as inexpensive therapeutic agent in prophylaxis as well as treatment of several infections. Tis review summarizes current knowledge on complex immune-modulatory role of vitamin D at cellular level as well as diferent mechanisms through which vitamin D exert protective role against diferent viral, bacterial, parasitic infections and non-infectious disorders. Research Article Muhammad Rehan 3 , Asim Aslam 3 , Javeria Umber 4 , Muti-ur-Rehman Khan 3 , Waqar Azeem 3 , Hassan Aftab 5 , Ahsan Anjum 3 , Muhammad Abid 6 , Abdul Hameed Khan 3 , Hafz Hasnain Ayoub 5 , Altaf Hussain 2 and Muhammad Farooq Khalid 1 * 1 Department of Animal nutrition Sub Campus Toba Tek Singh, University of Agriculture Faisalabad, Pakistan, 38000; 2 Department of Poultry Science University of Agriculture Faisalabad, Pakistan 38000; 3 Department of Pathology, University of Veterinary and Animal Sciences, Lahore, Pakistan-54000; 4 Department of Bioinformatics and Biotechnology, Government College University, Faisalabad, Pakistan; 5 Livestock and Dairy Development (L and DD), Punjab, Pakistan; 6 State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute (HVRI), Chinese Academy of Agricultural Sciences, Harbin 150001, PR China. Introduction F rom the mid of 17 th century, it was known that defciency of vitamin D resulted in several clinical disorders, but the exact cause remained mysterious until Adolf Windaus identifed link of vitamins with sterols ( Wolf, 2004). He won noble prize in 1928 in chemistry for detailed work on sterol constitution. Rickets was endemic in diferent parts of England but no one knows the exact causative agent until beginning Received | September 10, 2019; Accepted | October 23, 2019; Published | October 29, 2019 *Correspondence | Muhammad Farooq Khalid, Department of Animal Nutrition Sub Campus Toba Tek Singh, University of Agriculture Faisalabad, Pakistan, 38000; Email: farooq325@gmail.com DOI | http://dx.doi.org/10.17582/journal.hv/2019/6.5.115.129 Citation | Rehan, M., A. Aslam, J. Umber, M.R. Khan, W. Azeem, H. Aftab, A. Anjum, M. Abid, A.H. Khan, H.H. Ayoub, A. Hussain, M.F. Khalid. 2019. Immunomodulatory role of vitamin D in infectious and non-infectious diseases. Hosts and Viruses, 6(5): 115-129. Keywords: 1,25(OH) 2 D 3 , Adaptive immune response, Innate immunity, Immunomodulation, Infectious diseases, Non-infectious diseases Immunomodulatory Role of Vitamin D in Infectious and Non- Infectious Diseases