Effect of vitamin D3 on phagocytic potential of macrophages with live Mycobacterium tuberculosis and lymphoproliferative response in pulmonary tuberculosis

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, vitamin 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. tuberculosis 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 phagocytic potential and spontaneous lymphoproliferative response but brings down the antigen-induced response in normals. In tuberculosis, 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.