Mucosal associated invariant T (MAIT) cells are restricted by the monomorphic MHC class I‐like molecule, MHC‐related protein‐1 (MR1). Until 2012, the origin of the MAIT cell antigens (Ags) was ...unknown, although it was established that MAIT cells could be activated by a broad range of bacteria and yeasts, possibly suggesting a conserved Ag. Using a combination of protein chemistry, mass spectrometry, cellular biology, structural biology and small molecule chemistry, we discovered MR1 ligands derived from folic acid (vitamin B9) and from an intermediate in the microbial biosynthesis of riboflavin (vitamin B2). While the folate derivative 6‐formylpterin generally inhibited MAIT cell activation, two riboflavin pathway derivatives, 5‐(2‐oxopropylideneamino)‐6‐D‐ribitylaminouracil and 5‐(2‐oxoethylideneamino)‐6‐D‐ribitylaminouracil, were potent MAIT cell agonists. Other intermediates and derivatives of riboflavin synthesis displayed weak or no MAIT cell activation. Collectively, these studies revealed that in addition to peptide and lipid‐based Ags, small molecule natural product metabolites are also ligands that can activate T cells expressing αβ T‐cell receptors, and here we recount this discovery.
Mucosal associated invariant T (MAIT) cells are restricted by the monomorphic MHC class I‐like molecule, MHC‐related protein‐1 (MR1). Using a combination of protein chemistry, mass spectrometry, cellular biology, structural biology and chemistry, we discovered MAIT cell ligands derived from folic acid (vitamin B9) and from an intermediate in the microbial biosynthesis of riboflavin (vitamin B2). Collectively, these studies revealed that in addition to peptide and lipid‐based Ags, small molecule natural product metabolites are also ligands that can activate T cells expressing αβ T‐cell receptors, and here we recount this discovery.
Human MAIT cells sit at the interface between innate and adaptive immunity, are polyfunctional and are capable of killing pathogen infected cells via recognition of the Class IB molecule MR1. MAIT ...cells have recently been shown to possess an antiviral protective role in vivo and we therefore sought to explore this in relation to HIV-1 infection. There was marked activation of MAIT cells in vivo in HIV-1-infected individuals, which decreased following ART. Stimulation of THP1 monocytes with R5 tropic HIV
potently activated MAIT cells in vitro. This activation was dependent on IL-12 and IL-18 but was independent of the TCR. Upon activation, MAIT cells were able to upregulate granzyme B, IFNγ and HIV-1 restriction factors CCL3, 4, and 5. Restriction factors produced by MAIT cells inhibited HIV-1 infection of primary PBMCs and immortalized target cells in vitro. These data reveal MAIT cells to be an additional T cell population responding to HIV-1, with a potentially important role in controlling viral replication at mucosal sites.
Well over a hundred years ago, Professor Julius Bredt embarked on a career pursuing and critiquing bridged bicyclic systems that contained ring strain induced by the presence of a bridgehead olefin. ...These endeavors founded what we now know as Bredt’s rule (Bredtsche Regel). Physical, theoretical, and synthetic organic chemists have intensely studied this premise, pushing the boundaries of such systems to arrive at a better understood physical phenomenon. Mother nature has also seen fit to construct molecules containing bridgehead double bonds that encompass Bredt’s rule. For the first time, this topic is reviewed in a natural product context.
Bend it like Bredt: Bredt's rule, developed over a 100 years ago based on simple terpenes, states that the terminus of an olefin cannot exist at the bridgehead position of a bridged bicyclic system. For the first time, complex natural products containing bridgehead olefins and potential anti‐Bredt systems are reviewed and evaluated, yet should they be considered anti‐Bredt candidates at all?
Mucosal-associated invariant T (MAIT) cells are a unique innate-like T cell subset that responds to a wide array of bacteria and yeast through recognition of riboflavin metabolites presented by the ...MHC class I-like molecule MR1. Here, we demonstrate using MR1 tetramers that recipient MAIT cells are present in small but definable numbers in graft-versus-host disease (GVHD) target organs and protect from acute GVHD in the colon following bone marrow transplantation (BMT). Consistent with their preferential juxtaposition to microbial signals in the colon, recipient MAIT cells generate large amounts of IL-17A, promote gastrointestinal tract integrity, and limit the donor alloantigen presentation that in turn drives donor Th1 and Th17 expansion specifically in the colon after BMT. Allogeneic BMT recipients deficient in IL-17A also develop accelerated GVHD, suggesting MAIT cells likely regulate GVHD, at least in part, by the generation of this cytokine. Indeed, analysis of stool microbiota and colon tissue from IL-17A-/- and MR1-/- mice identified analogous shifts in microbiome operational taxonomic units (OTU) and mediators of barrier integrity that appear to represent pathways controlled by similar, IL-17A-dependent mechanisms. Thus, MAIT cells act to control barrier function to attenuate pathogenic T cell responses in the colon and, given their very high frequency in humans, likely represent an important population in clinical BMT.
MR1 is a highly conserved microbial immune-detection system in mammals. It captures vitamin B-related metabolite antigens from diverse microbes and presents them at the cell surface to stimulate ...MR1-restricted lymphocytes including mucosal-associated invariant T (MAIT) cells. MR1 presentation and MAIT cell recognition mediate homeostasis through host defense and tissue repair. The cellular mechanisms regulating MR1 cell surface expression are critical to its function and MAIT cell recognition, yet they are poorly defined. Here, we report that human MR1 is equipped with a tyrosine-based motif in its cytoplasmic domain that mediates low affinity binding with the endocytic adaptor protein 2 (AP2) complex. This interaction controls the kinetics of MR1 internalization from the cell surface and minimizes recycling. We propose MR1 uses AP2 endocytosis to define the duration of antigen presentation to MAIT cells and the detection of a microbial metabolic signature by the immune system.
Mucosal-associated invariant T (MAIT) cells are a subset of unconventional T cells that recognize small molecule metabolites presented by major histocompatibility complex class I related protein 1 ...(MR1), via an αβ T cell receptor (TCR). MAIT TCRs feature an essentially invariant TCR α-chain, which is highly conserved between mammals. Similarly, MR1 is the most highly conserved major histocompatibility complex-I–like molecule. This extreme conservation, including the mode of interaction between the MAIT TCR and MR1, has been shown to allow for species-mismatched reactivities unique in T cell biology, thereby allowing the use of selected species-mismatched MR1–antigen (MR1–Ag) tetramers in comparative immunology studies. However, the pattern of cross-reactivity of species-mismatched MR1–Ag tetramers in identifying MAIT cells in diverse species has not been formally assessed. We developed novel cattle and pig MR1–Ag tetramers and utilized these alongside previously developed human, mouse, and pig-tailed macaque MR1–Ag tetramers to characterize cross-species tetramer reactivities. MR1–Ag tetramers from each species identified T cell populations in distantly related species with specificity that was comparable to species-matched MR1–Ag tetramers. However, there were subtle differences in staining characteristics with practical implications for the accurate identification of MAIT cells. Pig MR1 is sufficiently conserved across species that pig MR1–Ag tetramers identified MAIT cells from the other species. However, MAIT cells in pigs were at the limits of phenotypic detection. In the absence of sheep MR1–Ag tetramers, a MAIT cell population in sheep blood was identified phenotypically, utilizing species-mismatched MR1–Ag tetramers. Collectively, our results validate the use and define the limitations of species-mismatched MR1–Ag tetramers in comparative immunology studies.
Mucosal‐associated invariant T (MAIT) cells are a major subset of innate‐like T cells mediating protection against bacterial infection through recognition of microbial metabolites derived from ...riboflavin biosynthesis. Mouse MAIT cells egress from the thymus as two main subpopulations with distinct functions, namely, T‐bet‐expressing MAIT1 and RORγt‐expressing MAIT17 cells. Previously, we reported that inducible T‐cell costimulator and interleukin (IL)‐23 provide essential signals for optimal MHC‐related protein 1 (MR1)‐dependent activation and expansion of MAIT17 cells in vivo. Here, in a model of tularemia, in which MAIT1 responses predominate, we demonstrate that IL‐12 and IL‐23 promote MAIT1 cell expansion during acute infection and that IL‐12 is indispensable for MAIT1 phenotype and function. Furthermore, we showed that the bias toward MAIT1 or MAIT17 responses we observed during different bacterial infections was determined and modulated by the balance between IL‐12 and IL‐23 and that these responses could be recapitulated by cytokine coadministration with antigen. Our results indicate a potential for tailored immunotherapeutic interventions via MAIT cell manipulation.
Mucosal‐associated invariant T (MAIT) cells in mice exist as two subsets: T‐bet‐expressing MAIT1 and RORγt‐expressing MAIT17 cells. We show that interleukin (IL)‐12 and IL‐23 promote MAIT1 cell expansion during acute infection with Francisella tularensis, and that the bias toward MAIT1 or MAIT17 responses seen during different bacterial infections is determined by the balance between these cytokines. Excitingly, these responses can be recapitulated by varying the ratio of cytokines coadministered with antigen, indicating a potential for therapeutic manipulation of MAIT cells.
The first total synthesis of vibsane-type diterpenoids neovibsanin G and 14-epi-neovibsanin G has been achieved. Key to this endeavour was a late stage EtAlCl(2) mediated skeletal rich cascade ...leading to the bicyclo3.3.1nonane core in one step.
The design and synthesis of potent inhibitors of purple acid phosphatase are reported.
Purple acid phosphatases (PAPs) are binuclear hydrolases that catalyse the hydrolysis of a range of ...phosphorylated substrates. Human PAP is a major histochemical marker for the diagnosis of osteoporosis. In patients suffering from this disorder, PAP activity contributes to increased bone resorption and, therefore, human PAP is a key target for the development of anti-osteoporotic drugs. This manuscript describes the design and synthesis of derivatives of 1-naphthylmethylphosphonic acids as inhibitors of PAP. The
K
i values of these compounds are as low as 4
μM, the lowest reported to date for a PAP inhibitor.
Introduction: The fertility preservation (FP) services offered in Hong Kong are underutilised. There have been no previous studies on Chinese medical students to investigate the underlying reasons ...for this underutilisation in terms of awareness, knowledge, and attitudes towards FP and age-related fertility. Methods: This was a cross-sectional survey among Chinese medical students in Hong Kong. Results: The majority of participants (77.8%) were not familiar with any clinics or specialists who provide FP services. The vast majority (88.1%) underestimated female infertility at age 45 years, and 89.8% overestimated the age of male fertility decline. The students’ FP knowledge was mainly acquired from electronic media (58.4%) and medical school (57.6%). Medical students showed overwhelming support towards FP for medical reasons (97.9%) but had mixed responses about FP for elective reasons related to career development in women (58.8%). Of the participants, 80.2% agreed that the government should subsidise FP services for patients with medical reasons. Conclusion: This study highlights the limited awareness and knowledge of FP among Chinese medical students. There is a strong worldwide need to increase education about and exposure to FP in the medical curriculum and improve medical students’ knowledge.
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