Vitamin D and macrophage functions in tuberculosis.

Selvaraj, P.; Afsal, K.; Harishankar, M.

Macrophage; 2015; 2; e756.         

Abstract: M ononuclear phagocytes like monocytes/macrophages engulf microbes and mediate intracellular killing through the activation of various antimicrobial activities such as synthesis of anti-microbial peptides, reactive oxygen/nitrogen intermediates and autophagy induction. However, intracellular pathogens like M. tuberculosis evade from macrophage defence mechanisms by various strategies to adapt the intracellular environment of macrophages and creating a major host cell niche for its growth and survival. 1, 25-dihydroxyvitamin D3 [1,25(OH) 2 D 3 ] is the active metabolite of vitamin D, which modulates immune functions mediated by monocytes, macrophages, dendritic cells, T cells and B cells. Genomic actions of 1, 25(OH) 2 D 3 ] exert through the vitamin D receptor, which is expressed constitutively in macrophages. Various studies have shown that 1,25(OH) 2 D 3 ] enhances the macrophage phagocytosis by upregulating the surface receptors including CD14 and mannose receptor. Moreover, 1,25(OH) 2 D 3 ] enhances the antimicrobial effects of macrophages by upregulating the expression of cathelicidin antimicrobial peptide and defensin, which inhibit the intracellular growth of M. tuberculosis . 1, 25(OH) 2 D 3 ] mediated cathelicidin expression upregulates the autophagy genes and enhance the fusion of phagosome containing M. tuberculosis with lysosome. Apart from antimicrobial effects, 1,25(OH) 2 D 3 ] also modulates the antigen presentation and secretion of chemokines, cytokines and other factors of macrophages. In conclusion, it has been suggested that 1,25(OH) 2 D 3 ] enhances macrophage innate immune functions by upregulating the antimicrobial efficiency, which could be beneficial to the host during active tuberculosis disease. In addition, during anti-TB treatment, nutritional supplementation of vitamin D could be helpful to minimize the inflammation at the site of infection.

Keywords: 1 ,25-dihydroxyvitamin D 3 ; Macrophages; Phagocytosis; Anti-microbial peptides; Immuno-modulation; Tuberculosis

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