Structural insight into MR1-mediated recognition of the mucosal associated invariant T cell receptor

Mucosal-associated invariant T (MAIT) cells express a semiinvariant αβ T cell receptor (TCR) that binds MHC class I-like molecule (MR1). However, the molecular basis for MAIT TCR recognition by MR1 is unknown. In this study, we present the crystal structure of a human Vα7.2Jα33-Vβ2 MAIT TCR. Mutagenesis revealed highly conserved requirements for the MAIT TCR-MR1 interaction across different human MAIT TCRs stimulated by distinct microbial sources. Individual residues within the MAIT TCR β chain were dispensable for the interaction with MR1, whereas the invariant MAIT TCR α chain controlled specificity through a small number of residues, which are conserved across species and located within the Vα-Jα regions. Mutagenesis of MR1 showed that only two residues, which were centrally positioned and on opposing sides of the antigen-binding cleft of MR1, were essential for MAIT cell activation. The mutagenesis data are consistent with a centrally located MAIT TCR-MR1 docking that was dominated by the α chain of the MAIT TCR. This candidate docking mode contrasts with that of the NKT TCR-CD1d-antigen interaction, in which both the α and β chain of the NKT TCR is required for ligation above the F\u27-pocket of CD1d

A structural basis for selection and cross-species reactivity of the semi-invariant NKT cell receptor in CD1d/glycolipid recognition

Little is known regarding the basis for selection of the semi-invariant αβ T cell receptor (TCR) expressed by natural killer T (NKT) cells or how this mediates recognition of CD1d–glycolipid complexes. We have determined the structures of two human NKT TCRs that differ in their CDR3β composition and length. Both TCRs contain a conserved, positively charged pocket at the ligand interface that is lined by residues from the invariant TCR α- and semi-invariant β-chains. The cavity is centrally located and ideally suited to interact with the exposed glycosyl head group of glycolipid antigens. Sequences common to mouse and human invariant NKT TCRs reveal a contiguous conserved “hot spot” that provides a basis for the reactivity of NKT cells across species. Structural and functional data suggest that the CDR3β loop provides a plasticity mechanism that accommodates recognition of a variety of glycolipid antigens presented by CD1d. We propose a model of NKT TCR–CD1d–glycolipid interaction in which the invariant CDR3α loop is predicted to play a major role in determining the inherent bias toward CD1d. The findings define a structural basis for the selection of the semi-invariant αβ TCR and the unique antigen specificity of NKT cells

Antigen-loaded MR1 tetramers define T cell receptor heterogeneity in mucosal-associated invariant T cells

Mucosal-associated invariant T cells (MAIT cells) express a semi-invariant T cell receptor (TCR) alpha-chain, TRAV1-2-TRAJ33, and are activated by vitamin B metabolites bound by the major histocompatibility complex (MHC)-related class I-like molecule, MR1. Understanding MAIT cell biology has been restrained by the lack of reagents to specifically identify and characterize these cells. Furthermore, the use of surrogate markers may misrepresent the MAIT cell population. We show that modified human MR1 tetramers loaded with the potent MAIT cell ligand, reduced 6-hydroxymethyl-8-D-ribityllumazine (rRL-6-CH2OH), specifically detect all human MAIT cells. Tetramer(+) MAIT subsets were predominantly CD8(+) or CD4(-)CD8(-), although a small subset of CD4(+) MAIT cells was also detected. Notably, most human CD8(+) MAIT cells were CD8 alpha(+)CD8 beta(-/lo), implying predominant expression of CD8 alpha alpha homodimers. Tetramer-sorted MAIT cells displayed a T(H)1 cytokine phenotype upon antigen-specific activation. Similarly, mouse MR1-rRL-6-CH2OH tetramers detected CD4(+), CD4(-)CD8(-) and CD8(+) MAIT cells in V. 19 transgenic mice. Both human and mouse MAIT cells expressed a broad TCR-beta repertoire, and although the majority of human MAIT cells expressed TRAV1-2-TRAJ33, some expressed TRAJ12 or TRAJ20 genes in conjunction with TRAV1-2. Accordingly, MR1 tetramers allow precise phenotypic characterization of human and mouse MAIT cells and revealed unanticipated TCR heterogeneity in this population

Mucosal-associated invariant T cells augment immunopathology and gastritis in chronic helicobacter pyloriInfection

Mucosal-associated invariant T (MAIT) cells produce inflammatory cytokines and cytotoxic granzymes in response to by-products of microbial riboflavin synthesis. Although MAIT cells are protective against some pathogens, we reasoned that they might contribute to pathology in chronic bacterial infection. We observed MAIT cells in proximity to Helicobacter pylori bacteria in human gastric tissue, and so, using MR1-tetramers, we examined whether MAIT cells contribute to chronic gastritis in a mouse H. pylori SS1 infection model. Following infection, MAIT cells accumulated to high numbers in the gastric mucosa of wild-type C57BL/6 mice, and this was even more pronounced in MAIT TCR transgenic mice or in C57BL/6 mice where MAIT cells were preprimed by Ag exposure or prior infection. Gastric MAIT cells possessed an effector memory Tc1/Tc17 phenotype, and were associated with accelerated gastritis characterized by augmented recruitment of neutrophils, macrophages, dendritic cells, eosinophils, and non-MAIT T cells and by marked gastric atrophy. Similarly treated MR1−/− mice, which lack MAIT cells, showed significantly less gastric pathology. Thus, we demonstrate the pathogenic potential of MAIT cells in Helicobacter-associated immunopathology, with implications for other chronic bacterial infections

Drugs and drug-like molecules can modulate the function of mucosal-associated invariant T cells

The major-histocompatibility-complex-(MHC)-class-I-related molecule MR1 can present activating and non-activating vitamin-B-based ligands to mucosal-associated invariant T cells (MAIT cells). Whether MR1 binds other ligands is unknown. Here we identified a range of small organic molecules, drugs, drug metabolites and drug-like molecules, including salicylates and diclofenac, as MR1-binding ligands. Some of these ligands inhibited MAIT cells ex vivo and in vivo, while others, including diclofenac metabolites, were agonists. Crystal structures of a T cell antigen receptor (TCR) from a MAIT cell in complex with MR1 bound to the non-stimulatory and stimulatory compounds showed distinct ligand orientations and contacts within MR1, which highlighted the versatility of the MR1 binding pocket. The findings demonstrated that MR1 was able to capture chemically diverse structures, spanning mono- and bicyclic compounds, that either inhibited or activated MAIT cells. This indicated that drugs and drug-like molecules can modulate MAIT cell function in mammals

Development of a diagnostic test for the prediction and prevention of HLA-B57/B58-linked drug hypersensitivities

© 2014 Lyudmila KostenkoHLA-B*57:01 is strongly associated with a life-threatening hypersensitivity to the HIV drug abacavir, liver toxicity from the antibiotic flucloxacillin and is a marker for the slow progression of HIV infection to AIDS. HLA-B*58:01 is associated with Stevens-Johnson syndrome and Toxic Epidermal Necrolysis caused by drug allopurinol, used to treat hyperuricaemia and recurrent gout. Treatment and management of these drug reactions is complex and costly and is not always available. It is therefore of paramount importance to predict and prevent these drug reactions using fast and reliable laboratory methods. Whilst there are multiple techniques to determine an individual’s HLA type in the clinical transplantation setting, these methods are usually complex, time consuming and are not cost-effective. A quick, inexpensive and easy to carry out method, which provides a yes or a no answer, could be a more efficient way to detect HLA-B57 and B58 with an aim to predict and prevent drug-associated hypersensitivity. This thesis presents the generation of HLA-B57/B58-specific monoclonal antibody (mAb), 3E12, and its implementation in a flow cytometry-based approach. The usefulness of HLA-B57 screening for the prediction of abacavir hypersensitivity was evaluated in three independent laboratories, including confirmation of the mAb sensitivity and specificity in a cohort of patients enrolled in the international PREDICT-1 trial. The data shows that patients who test negative by mAb screening comprise 90%–95% of all individuals in most human populations and thus require no further HLA typing. Patients who test positive by mAb screening should proceed to high-resolution typing to confirm the presence of HLA-B*57:01 or HLA-B*58:01. Hence, mAb screening provides a fast and low-cost alternative to high-resolution typing of all patients and lends itself to point-of-care diagnostics and rapid ascertainment of low-risk patients who can begin immediate therapy with abacavir, flucloxacillin or allopurinol

ФОРМУВАННЯ ІНТЕРЕСУ ДО ВОКАЛЬНО-ХОРОВОЇ ДІЯЛЬНОСТІ

The article is devoted to the problem of interest formation in vocal and choral activity; the results of approaches that aimed to define and clarify the concept of "interest" and "motivation" in the psychology and pedagogy field is highlighted; the essence of cognitive interest as one of the most significant motives of studying, the formation of which creates a reliable and solid basis for a schoolchild’s personality development is disclosed; the current problems of reducing schoolchildren interest in the educational process and effective ways to solve them are presented; it is determined that one of the effective means of forming the interest and organization vocal and choral activity in school of arts is the music didactic game. The article presents the results of the statement section of the formation level of interest in vocal-choral activity of students of arts schools was carried out. Members of children’s choirs in Nizhyn took part in the research, namely: schoolchildren of the junior choir "Prominets", pupils of the senior choir "Siajvo" of the Children’s Music School and singers of the junior choir "Soniashnyk", schoolchildren of the senior choir "Lileja" of the School of Arts. Based on its results, pedagogical conditions for the formation of interestin vocal and choral activity are given.Стаття присвячена проблемі формування інтересу до вокально-хорової діяльності; розкрита сутність пізнавального інтересу як одного з найбільш значущих мотивів навчання, проаналізовані загальні причини зниження зацікавленості учнів до навчального процесу та визначені педагогічні умови їх вирішення

The production, purification and crystallization of a soluble form of the nonclassical MHC HLA-G: the essential role of cobalt

X-ray diffraction data were collected to 1.9 Å from crystals of HLA-G. Cobalt ions were found to be essential for the production of diffracting crystals

Використання цифрових ігор у професійній підготовці соціальних педагогів: реалії та перспективи

The article presents the possibilities of using digital games in the process of professional training of social educators. It was found that for the development of digital game-centered learning it is necessary to combine the efforts of public, private, charitable and public institutions and organizations that prepare for game design, training, organize exhibitions, competitions, festivals, which is the main direction of modern education as an important component. Competencies of the 21st century were talked about. It is determined that the use of computer games enhances the freedom of experiment, identity and social rewards, deepens personal experience by developing three basic needs for training motivation: competence (student feels the process of acquiring new knowledge and skills); autonomy (the student feels control over the educational process); interconnectedness (the student feels the connection with colleagues during the educational process). It is proved that the use of digital games in the professional training of social educators is an innovative and promising vector for the modernization of the educational process in modern higher education institutions as a whole.У статті наведено можливості використання цифрових ігор у процесі професійної підготовки соціальних педагогів. Виявлено, що для розвитку цифрового ігрового навчання необхідно об'єднання зусиль державних, приватних, благодійних та громадських установ та організацій, які здійснюють підготовку до геймдизайну, навчання, організацію виставок, конкурсів, фестивалів, що є основним напрямом сучасної освіти як важлива складова. Говорили про компетенції 21 століття. Визначено, що використання комп'ютерних ігор сприяє розширенню свободи експерименту, самобутності та соціальної винагороди, поглибленню особистого досвіду за рахунок розвитку трьох основних потреб мотивації навчання: компетентності (учень відчуває процес набуття нових знань та умінь); автономність (учень відчуває контроль за навчальним процесом); взаємопов'язаність (учень відчуває зв'язок із колегами у процесі навчання). Доведено, що використання цифрових ігор у професійній підготовці соціальних педагогів є інноваційним та перспективним вектором модернізації освітнього процесу у сучасних вищих навчальних закладах загалом