Natural killer (NK) cells are traditionally considered as innate cells but recent studies suggest that NK cells can distinguish antigens, and that memory NK cells expand and protect against viral pathogens. Limited information is available about the mechanisms involved in memory-like NK cell expansion, and their role in bacterial infections and vaccine-induced protective immune responses. In the current study, using a mouse model of tuberculosis (TB) infection, we found that IFN-γ producing CD3-NKp46+CD27+KLRG1+ memory-like NK cells develop during Bacille Calmette-Guerin (BCG) vaccination, expand and provide protection against challenge with Mycobacterium tuberculosis (M. tb). Using antibodies, siRNA and gene-deleted mice, we found that expansion of memory-like NK cells depends on IL-21. NKp46+CD27+KLRG1+ NK cells expanded in healthy individuals with latent TB infection (LTBI) in IL-21 dependent fashion. Our study provides first evidence that memory-like NK cells survive long term, expansion depends on IL-21 and involved in vaccine induced protective immunity against a bacterial pathogen.

Previously, we found that interleukin 22 (IL-22) inhibits intracellular growth of Mycobacterium tuberculosis in human monocyte-derived macrophages (MDMs). In the current study, we determined the mechanisms underlying these effects. We found that W7, a phagolysosomal fusion inhibitor, abrogates IL-22-dependent M. tuberculosis growth inhibition in MDMs, suggesting that IL-22 acts through enhanced phagolysosomal fusion. Our microarray analysis indicated that recombinant IL-22 (rIL-22) enhances the expression of an intracellular signaling molecule, calgranulin A. This was confirmed by real-time polymerase chain reaction, Western blot, and confocal microscopy. Calgranulin A small interfering RNA (siRNA) abrogated rIL-22-dependent growth inhibition of M. tuberculosis in MDMs. IL-22 enhanced Rab7 expression and downregulated Rab14 expression of M. tuberculosis-infected MDMs, and these effects were reversed by calgranulin A siRNA. These results suggest that M. tuberculosis growth inhibition by IL-22 depends on calgranulin A and enhanced phagolysosomal fusion, which is associated with increased Rab7 and reduced Rab14 expression.

In this study, we developed a mouse model of type 2 diabetes mellitus (T2DM) using streptozotocin and nicotinamide and identified factors that increase susceptibility of T2DM mice to infection by Mycobacterium tuberculosis (Mtb). All Mtb-infected T2DM mice and 40% of uninfected T2DM mice died within 10 months, whereas all control mice survived. In Mtb-infected mice, T2DM increased the bacterial burden and pro- and anti-inflammatory cytokine and chemokine production in the lungs relative to those in uninfected T2DM mice and infected control mice. Levels of IL-6 also increased. Anti-IL-6 monoclonal antibody treatment of Mtb-infected acute- and chronic-T2DM mice increased survival (to 100%) and reduced pro- and anti-inflammatory cytokine expression. CD11c+ cells were the major source of IL-6 in Mtb-infected T2DM mice. Pulmonary natural killer (NK) cells in Mtb-infected T2DM mice further increased IL-6 production by autologous CD11c+ cells through their activating receptors. Anti-NK1.1 antibody treatment of Mtb-infected acute-T2DM mice increased survival and reduced pro- and anti-inflammatory cytokine expression. Furthermore, IL-6 increased inflammatory cytokine production by T lymphocytes in pulmonary tuberculosis patients with T2DM. Overall, the results suggest that NK-CD11c+ cell interactions increase IL-6 production, which in turn drives the pathological immune response and mortality associated with Mtb infection in diabetic mice.

SUMMARY We studied the factors that regulate IL-23 receptor expression and IL-17 production in human tuberculosis infection. Mycobacterium tuberculosis (M. tb)-stimulated CD4+ cells from tuberculosis patients secreted less IL-17 than did CD4+ cells from healthy tuberculin reactors (PPD+). M. tb cultured monocytes from tuberculosis patients and PPD+ donors expressed equal amounts of IL-23p19 mRNA and protein, suggesting that reduced IL-23 production is not responsible for decreased IL-17 production by tuberculosis patients. Freshly isolated and M. tb- stimulated CD4+ cells from tuberculosis patients had reduced IL-23 receptor and phosphorylated STAT3 (pSTAT3) expression, compared to PPD+ donors. STAT3 siRNA reduced IL-23 receptor expression, and IL-17 production by CD4+ cells from PPD+ donors. Tuberculosis patients had increased number of PD-1+ T cells compared to healthy PPD+ individuals. Anti-PD-1 antibody enhanced pSTAT3 and IL-23R expression and IL-17 production by M. tb cultured CD4+ cells of tuberculosis patients. Anti-tuberculosis therapy decreased PD-1 expression, increased IL-17 and IFN-γ production and pSTAT3, IL-23R expression. These findings demonstrate that increased PD-1 expression and decreased pSTAT3 expression reduces IL-23 receptor expression and IL-17 production by CD4+ cells of tuberculosis patients.

Objective: Pulmonary tuberculosis (PTB) is a leading cause of morbidity and mortality. Macrophages play an important role in the immunopathogenesis of tuberculosis. Extracellular ATP induces macrophage bactericidal activity through activation of the purinergic P2X7 receptor. This case- control study assesses the association of −762 T/C, 1513A/C and 1729T/A P2X7 polymorphisms in patients with PTB and healthy controls to establish association if any with risk of developing the disease. Materials and methods: The genotyping for P2X7 was carried out using PCR and RFLP analysis in 256 individuals, which included 156 active PTB patients and 100 age and sex, matched healthy volunteers with no clinical symptoms or family history of PTB as controls. Results: A chi square test showed a significant difference between the PTB patient and controls for −762 C allele; p=0.0051 (OR 1.6972, CI 95% 1.1839 to 2.4332) and1729 T allele was found to be positively associated with the PTB; p < 0.0005 (OR-2.4623, CI 95% 1.6376 to 3.7022). 1513A/C polymorphism did not show any significant difference between the two groups. Significance: The study revealed a significant association of P2X7-762C allele and P2X7 1729T allele receptor polymorphisms with PTB in Asian Indian population. The use of these alleles as biomarkers for identifying individuals at high risk of developing TB needs to be ascertained.