TLR2 Regulates Mast Cell IL-6 and IL-13 Production During Listeria monocytogenes Infection

Listeria monocytogenes (L.m) is efficiently controlled by several cells of the innate immunity, including the Mast Cell (MC). MC is activated by L.m inducing its degranulation, cytokine production and microbicidal mechanisms. TLR2 is required for the optimal control of L.m infection by different cells of the immune system. However, little is known about the MC receptors involved in recognizing this bacterium and whether these interactions mediate MC activation. In this study, we analyzed whether TLR2 is involved in mediating different MC activation responses during L.m infection. We found that despite MC were infected with L.m, they were able to clear the bacterial load. In addition, MC degranulated and produced ROS, TNF-α, IL-1β, IL-6, IL-13 and MCP-1 in response to bacterial infection. Interestingly, L.m induced the activation of signaling proteins: ERK, p38 and NF-κB. When TLR2 was blocked, L.m endocytosis, bactericidal activity, ROS production and mast cell degranulation were not affected. Interestingly, only IL-6 and IL-13 production were affected when TLR2 was inhibited in response to L.m infection. Furthermore, p38 activation depended on TLR2, but not ERK or NF-κB activation. These results indicate that TLR2 mediates only some MC activation pathways during L.m infection, mainly those related to IL-6 and IL-13 production.

Autophagy induced by human neutrophil exovesicles controls intracellular growth of Mycobacterium tuberculosis H37Rv in autologous macrophages

We have previously shown that human neutrophils (NEU) stimulated with live Mycobacterium tuberculosis H37Rv (Mtb) release exovesicles, named EXO-Mtb. When autologous macrophages were incubated with EXO-Mtb, they increased the expression of CD86 and MHC II and produced inflammatory cytokines. Here we demonstrate that EXO-Mtb can also reduce the intracellular load of Mtb in autologous macrophages. Since autophagy has been shown to control mycobacterial growth, LC3II expression was measured on infected macrophages after incubation with EXO-Mtb (4, 6 and 24h). Control EXO preparations included those released spontaneously from NEU, or after stimulation with PMA or fMLP. Our results showed that of all EXO preparations used, EXO-Mtb induced the largest amounts of LC3II protein, which correlates with a significant reduction of colony forming units (CFU). This phenomenon could be reverted with the addition of Wortmannin, an autophagy inhibitor. It is important to remark that there was not a 100% control of intracellular mycobacterial growth. Further experiments should be done to better understand the role of ectosomes in NEU-macrophage communication through exovesicles.

Analysis of extrinsic pathway mediators in CD8+CD38+ T cells of healthy donors stimulated with Mycobacterium tuberculosis antigens (99.20)

CD38 is expressed in human T cells during early stages of activation and differentiation and can be used as a marker of prognosis for HIV. Currently, CD38 has raised interest since it has been found increased in patients with tuberculosis, however when the active phase is solved a decrease of CD38 in CD8 T lymphocytes is observed. Here we evaluated and determined the role of CD38 in human CD8 T lymphocytes stimulated with M. tuberculosis H37Rv soluble extracts (MTSE) and delipidized MTSE (dMTSE) in vitro. For this purpose, PBMC from healthy donors were incubated with PMA-ionomicyne, media, MTSE or dMTSE. After cultured, cells were harvested and stained with monoclonal antibodies conjugated to different fluorochromes. After kinetics experiments were performed and the expression of perforin, granzyme A, IFN-γ and CD38 in T CD8 cells was determined by flow cytometry. Expression of IFN-γ and perforin was statistically higher in T CD8+CD38+ in comparison with T CD8+CD38-. Remarkably, CD8+CD38+ T cells showed an increased cytotoxicity against macrophages pulsed with MTSE. These results suggest that the population of T CD8+ lymphocytes might have an effector functions in Ag specific dependance on CD38. This is the first report linking CTL activity to the CD38 molecule in tuberculosis.