on of surface MHC class II expression on macrophages and changes in the profile of cytokines and chemokines in DCs that individually and collectively affect priming of T cells. Other modulations include downregulation of reactive nitrogen and reactive oxygen species generation, inhibition of IFN-c receptor expression and activation on macrophages. A number of immune evasive effects of M. tuberculosis are reproduced by specific M. tuberculosis antigens. These include inhibition of IFN-c and Toll Like Receptor pathways by 19 kDa lipoprotein, inhibition of NF-kB activation and IL-12 production by mannosylated lipoarabinomanan mediated activation of DC-SIGN. On similar lines, we have also demonstrated the immuno-suppressive effects of CFP-10 that mediates its effects by inducing differentiation of DCs that confer suppressor responses. Calcium plays a key role in regulating many of the modulations that are targeted by M. tuberculosis for immune evasion. For example, calcium regulates the activities of calmodulin and sphingosine kinase that affects M. tuberculosis survival; and calcinuerin that regulates the expression of coronin-1 on phagosomes thus affecting phagosome maturation. In addition, calcium concentrations 
and kinetics directly affect the activation of transcription 64048-12-0 factors such as NF-AT and NF-kB leading to differential cytokine expression and this governs the quantum and quality of immune responses. As described earlier, 22431203 calcium influx in mammalian cells is stage dependent, initiating with the depletion of intracellular stores followed by opening up of various channels. Although, VGCC have been shown to play major roles in physiological responses, their roles in infectious diseases have recently assumed importance. For Ca Channels and Mycobacteria example, L-type VGCC has been demonstrated to play roles in regulating intracellular growth of Legionella pneumophila and in induction of calcium in CD4+ T cells during Leishmania infection. Therefore, in the present study, we investigated the roles of Ltype and R-type VGCC in mediating protective responses during M. tuberculosis infection. Our results showed that inhibiting or blocking L-type and R-type VGCC in DCs, macrophages and human PBMCs increased intracellular calcium concentration. This indicated a negative role for L-type and R-type VGCC in calcium influx in the context of M. tuberculosis infection. L-type VGCC has been previously reported to play a negative role in calcium induction wherein the knockdown of its beta subunit in mouse results in increased frequency of calcium oscillations leading to increased insulin secretion in beta cells. In addition, blocking L-type and R-type VGCC increased the expression and kinetics of a number of cytokines and transcription factors that promote pro-inflammatory responses. Several reports indicate a role for VGCC in regulating the activation of transcription factors. For example, L-type VGCC has been shown to be 10604535 essential for CREB phosphorylation and activation of c-fos. We next showed that L-type and R-type VGCC directly affected survival of M. tuberculosis. Blocking L-type and R-type VGCC in macrophages or PBMCs resulted in killing of M. tuberculosis. Blocking L-type and R-type VGCC in DCs, primed T cells that mediated killing of M. tuberculosis inside macrophages. The fact that M. tuberculosis killing was better than that obtained by IFN-c treatment indicates that blocking L-type and R-type VGCC could bypass the suppressive effects of
