Journal of Clinical Immunology, Vol. 24, No. 3, May 2004 ( C  2004) Effect of Vitamin D 3 on Phagocytic Potential of Macrophages with Live Mycobacterium tuberculosis and Lymphoproliferative Response in Pulmonary Tuberculosis G. CHANDRA, 1 P. SELVARAJ, 1,2 M. S. JAWAHAR, 1 V. V. BANUREKHA, 1 and P. R. NARAYANAN 1 Accepted: November 18, 2003 Immune responses are elicited through antigen presentation and recognition by macrophages and T-lymphocytes, respectively. The immunomodulatory effect of vitamin D 3 on macrophage phagocytic potential with live Mycobacterium tuberculosis, spontaneous and M. tuberculosis culture filtrate antigen induced lymphocyte responses were studied in pulmonary tuberculosis patients (PTBPs) (n = 31) and normal healthy subjects (NHSs) (n = 43). Vitamin D 3 at a concentration of 10 −7 M significantly enhanced the macrophage phagocytosis of live M. tuberculosis in normal subjects with low phagocytic potential (less than 10%) ( p = 0.015). No such increase was observed in PTBPs. Vitamin D 3 significantly decreased the spontaneous lymphoproliferative response ( p = 0.022) and increased the apoptosis of peripheral blood mononuclear cells in PTBPs ( p = 0.024). In normals, vita- min D 3 increased the spontaneous lymphoproliferative response. An inverse correlation between macrophage phagocytosis and spontaneous response was observed in NHSs, whereas a direct correlation was seen between vitamin D 3 -treated cells in normal subjects under in vitro condition. Vitamin D 3 decreased the M. tu- berculosis culture filtrate antigen induced lymphocyte response significantly in normal subjects ( p = 0.0003), while it had no influence on the lymphocyte response in PTBPs. The present study suggests that exposure to vitamin D 3 increases the phago- cytic potential and spontaneous lymphoproliferative response but brings down the antigen-induced response in normals. In tu- berculosis, addition of vitamin D 3 has no significant effect on antigen-induced lymphoproliferative response. This may be due to the unresponsive nature of the cells to the action of vitamin D 3 by virtue of the disease, which renders them inactive. KEY WORDS: Vit. D 3 ; macrophages; phagocytosis; lymphoprolifera- tion; M. tuberculosis; pulmonary TB. 1 Tuberculosis Research Centre, Indian Council of Medical Research, Chennai, India. 2 To whom correspondence should be addressed at Department of Immunology, Tuberculosis Research Centre (ICMR), Mayor V.R. Ramanathan Road, Chetput, Chennai 600 031, India; e-mail: psraj21@hotmail.com. INTRODUCTION Tuberculosis (TB) is a granulomatous disease caused by Mycobacterium tuberculosis. Although, one third of the world population is infected with M. tuberculosis, fewer than 10% ever develop tuberculosis (1). The immune sys- tem is highly effective in containing the pathogen, but fails to eradicate it. The immune response to TB is cell mediated, involving players like the macrophages, T-cell subsets, and cytokines. M. tuberculosis is an intracellu- lar pathogen, with the ability to persist in macrophages by successfully evading its bactericidal and bacteriostatic mechanisms. Prior to the availability of antituberculosis drugs, vi- tamin D (vit. D) was used in the treatment of patients with cutaneous tuberculosis and was reported to have dra- matic effects (2). 1α,25-Dihydroxyvitamin D 3 (vit. D 3 ) is a steroid hormone involved in bone mineral metabolism and plays an important role in causing hypercalcaemia in granulomatous diseases such as tuberculosis and sar- coidosis (3). Hypercalcaemia in tuberculosis is character- ized by its presence during the active phase of the disease (4–8). The incidence of hypercalcaemia in tuberculosis ranges from 15 to 51% among various countries (4, 7– 11). The incidence rate is suggested to be due to the dif- ferences in the vit. D and calcium intake, the amount of exposure to the sun, the extent of disease and the criteria for hypercalcaemia (5, 10–13). Increased endogenous vit. D 3 production by activated alveolar macrophages is also suggested to be one of the reasons for hypercalcaemia in tuberculosis. Activated macrophages possess the enzyme 1α-hydroxylase that allows the production of vit. D 3 (14). The abnormalities associated with calcium metabolism in tuberculosis are suggested to be due to dysregulated pro- duction of vit. D 3 by activated macrophages and T lym- phocytes trapped in pulmonary alveoli and granulomatous inflammation (3, 15, 16). 249 0271-9142/04/0500-0249/0 C  2004 Plenum Publishing Corporation