Immunology
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Mucosal-associated invariant T (MAIT) cells are donor-unrestricted lymphocytes that are surprisingly abundant in humans, representing 1-10% of circulating T cells and further enriched in mucosal tissues. MAIT cells recognize and are activated by small molecule ligands produced by microbes and presented by MR1, a highly conserved MHC-related antigen-presenting protein that is ubiquitously expressed in human cells. Increasing evidence suggests that MAIT cells play a protective role in anti-bacterial immunity at mucosal interfaces. ⋯ Many questions remain unanswered about the potential of MAIT cells for protection or pathogenesis in infectious diseases. Because they interact with the universal, donor-unrestricted ligand-presenting MR1 molecule, MAIT cells may be attractive immunotherapy or vaccine targets. New tools, including the development of MR1-ligand tetramers and next-generation T-cell receptor sequencing, have the potential to accelerate MAIT cell research and lead to new insights into the role of this unique set of lymphocytes in infectious diseases.
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Human respiratory syncytial virus (hRSV) is the leading cause of infant hospitalization related to respiratory disease. Infection with hRSV produces abundant infiltration of immune cells into the airways, which combined with an exacerbated pro-inflammatory immune response can lead to significant damage to the lungs. Human RSV re-infection is extremely frequent, suggesting that this virus may have evolved molecular mechanisms that interfere with host adaptive immunity. ⋯ Remarkably, we also observed that in the absence of hRSV-specific antibodies FcγRIII knockout mice displayed significantly less cellular infiltration in the lungs after hRSV infection, compared with wild-type mice, suggesting a potentially harmful, IgG-independent role for this receptor in hRSV disease. Our findings support the notion that FcγRs can contribute significantly to the modulation of DC function by hRSV and hRSV-IC. Further, we provide evidence for an involvement of FcγRIII in the development of hRSV pathogenesis.
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Although bacillus Calmette-Guérin (BCG) is an established vaccine with excellent efficacy against disseminated Mycobacterium tuberculosis infection in young children, efficacy in adults suffering from respiratory tuberculosis (TB) is suboptimal. Prime-boost viral vectored vaccines have been shown to induce effective immune responses and lentivectors (LV) have been shown to improve mucosal immunity in the lung. A mucosal boost to induce local immunogenicity is also referred to as a 'pull' in a prime and pull approach, which has been found to be a promising vaccine strategy. ⋯ Prime and pull immunization with LV85A induced significantly enhanced CD8(+) and CD4(+) T-cell responses in the lung, but did not protect against intranasal BCG challenge. In contrast, little T-cell response in the lung was seen when the prime vaccine was BCG, and intranasal vF/85A provided no additional protection against mucosal BCG infection. Our study demonstrates that not all LV prime and pull approaches may be successful against TB in man and careful antigen and immune activator selection is therefore required.
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Over one million newborns die annually from sepsis with the highest mortality in premature and low-birthweight infants. The inflammasome plays a central role in the regulation of innate immunity and inflammation, and is presumed to be involved in protective immunity, in large part through the caspase-1-dependent activation of interleukin-1β (IL-1β) and IL-18. Studies in endotoxic shock, however, suggest that endogenous caspase-1 activity and the inflammasome contribute to mortality primarily by promoting excessive systemic inflammatory responses. ⋯ Surprisingly, caspase-1/11(-/-) neonates also exhibited increased bone marrow and splenic haematopoietic stem cell expansion (P < 0·001), and increased concentrations of granulocyte and macrophage colony-stimulating factors in the peritoneum (P < 0·001) after sepsis. Ablation of caspase-1/11 signalling was also associated with increased recruitment of peritoneal macrophages and neutrophils (P < 0·001), increased phagocytosis by neutrophils (P = 0·003), and decreased bacterial colonization (P = 0·02) in the peritoneum. These findings suggest that endogenous caspase-1/11 activity, independent of the NLRP3 inflammasome, not only promotes the magnitude of the inflammatory response, but also suppresses protective immunity in the neonate, so contributing to innate immune dysfunction and poor survival in neonatal sepsis.
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As part of the innate immune response, neutrophils are at the forefront of defence against infection, resolution of inflammation and wound healing. They are the most abundant leucocytes in the peripheral blood, have a short lifespan and an estimated turnover of 10(10) to 10(11) cells per day. Neutrophils efficiently clear microbial infections by phagocytosis and by oxygen-dependent and oxygen-independent mechanisms. ⋯ Here it is shown that NETs formation is strictly dependent on glucose and to a lesser extent on glutamine, that Glut-1, glucose uptake, and glycolysis rate increase upon PMA stimulation, and that NET formation is inhibited by the glycolysis inhibitor, 2-deoxy-glucose, and to a lesser extent by the ATP synthase inhibitor oligomycin. Moreover, when neutrophils were exposed to PMA in glucose-free medium for 3 hr, they lost their characteristic polymorphic nuclei but did not release NETs. However, if glucose (but not pyruvate) was added at this time, NET release took place within minutes, suggesting that NET formation could be metabolically divided into two phases; the first, independent from exogenous glucose (chromatin decondensation) and, the second (NET release), strictly dependent on exogenous glucose and glycolysis.