Antigen Presentation by MHC Class I and CD1 Molecules

Antigen presentation is the “sine qua non” of the mammalian adaptive immune system. The assembly of MHC class I/peptide complexes in the endoplasmic reticulum (ER) relies on the orchestrated interplay between different chaperonins, which assist MHC class I folding, and the peptide loading complex (PLC). Mutant lymphoblastoid cell lines with defective MHC class I surface expression have greatly helped the functional analysis of the PLC. The TAP transporter associated with antigen processing translocates MHC class I peptide ligands from the cytosol into the ER and is critical for successful MHC class I assembly and maturation. In the first two results chapters of this thesis I will describe the identification, clinical description and molecular and genetic analysis of a new clinical syndrome in a group of patients with dramatically reduced MHC class I surface expression. The disease in these patients could be identified as primary TAP-deficiency. Mycobacterial infections were conspicuously absent in these TAP-deficient patients whereas TAP-deficient mice are known to be highly susceptible to mycobacteria. The focus of the third and fourth chapter of this thesis lies on lipid antigen presentation via CD1 molecules, which are known to present mycobacterial lipids to T lymphocytes. The first objective of this thesis was to generate recombinant mycobacterial lipid loaded CD1 molecules as tools to measure mycobacterial lipid specific T cell responses in the TAP-deficient patients. Chapters three and four describe novel protocols for the generation of recombinant human CD 1b and CD 1d molecules with loaded single lipid species

Innate and adaptive T cells in asthmatic patients: relationship to severity and disease mechanisms

BackgroundAsthma is a chronic inflammatory disease involving diverse cells and mediators whose interconnectivity and relationships to asthma severity are unclear.ObjectiveWe performed a comprehensive assessment of TH17 cells, regulatory T cells, mucosal-associated invariant T (MAIT) cells, other T-cell subsets, and granulocyte mediators in asthmatic patients.MethodsSixty patients with mild-to-severe asthma and 24 control subjects underwent detailed clinical assessment and provided induced sputum, endobronchial biopsy, bronchoalveolar lavage, and blood samples. Adaptive and invariant T-cell subsets, cytokines, mast cells, and basophil mediators were analyzed.ResultsSignificant heterogeneity of T-cell phenotypes was observed, with levels of IL-13–secreting T cells and type 2 cytokines increased at some, but not all, asthma severities. TH17 cells and ??-17 cells, proposed drivers of neutrophilic inflammation, were not strongly associated with asthma, even in severe neutrophilic forms. MAIT cell frequencies were strikingly reduced in both blood and lung tissue in relation to corticosteroid therapy and vitamin D levels, especially in patients with severe asthma in whom bronchoalveolar lavage regulatory T-cell numbers were also reduced. Bayesian network analysis identified complex relationships between pathobiologic and clinical parameters. Topological data analysis identified 6 novel clusters that are associated with diverse underlying disease mechanisms, with increased mast cell mediator levels in patients with severe asthma both in its atopic (type 2 cytokine–high) and nonatopic forms.ConclusionThe evidence for a role for TH17 cells in patients with severe asthma is limited. Severe asthma is associated with a striking deficiency of MAIT cells and high mast cell mediator levels. This study provides proof of concept for disease mechanistic networks in asthmatic patients with clusters that could inform the development of new therapies

Oral abstracts 1: SpondyloarthropathiesO1. Detecting axial spondyloarthritis amongst primary care back pain referrals

Background: Inflammatory back pain (IBP) is an early feature of ankylosing spondylitis (AS) and its detection offers the prospect of early diagnosis of AS. However, since back pain is very common but only a very small minority of back pain sufferers have ASpA or AS, screening of back pain sufferers for AS is problematic. In early disease radiographs are often normal so that fulfilment of diagnostic criteria for AS is impossible though a diagnosis of axial SpA can be made if MRI evidence of sacroiliitis is present. This pilot study was designed to indicate whether a cost-effective pick up rate for ASpA/early AS could be achieved by identifying adults with IBP stratified on the basis of age. Methods: Patients aged between 18 and 45 years who were referred to a hospital physiotherapy service with back pain of more than 3 months duration were assessed for IBP. All were asked to complete a questionnaire based on the Berlin IBP criteria. Those who fulfilled IBP criteria were also asked to complete a second short questionnaire enquiring about SpA comorbidities, to have a blood test for HLA-B27 and CRP level and to undergo an MRI scan of the sacroiliac joints. This was a limited scan, using STIR, diffusion-weighted, T1 and T2 sequences of the sacroiliac joints to minimize time in the scanner and cost. The study was funded by a research grant from Abbott Laboratories Ltd. Results: 50 sequential patients agreed to participate in the study and completed the IBP questionnaire. Of these 27 (54%) fulfilled criteria for IBP. Of these, 2 patients reported a history of an SpA comorbidity - 1 psoriasis; 1 ulcerative colitis - and 3 reported a family history of an SpA comorbidity - 2 psoriasis; 1 Crohn's disease. 4 were HLA-B27 positive, though results were not available for 7. Two patients had marginally raised CRP levels (6, 10 -NR ≤ 5). 19 agreed to undergo MRI scanning of the sacroiliac joints and lumbar spine; 4 scans were abnormal, showing evidence of bilateral sacroiliitis on STIR sequences. In all cases the changes met ASAS criteria but were limited. Of these 4 patients 3 were HLA-B27 positive but none gave a personal or family history of an SpA-associated comorbidity and all had normal CRP levels. Conclusions: This was a pilot study yielding only limited conclusions. However, it is clear that: Screening of patients referred for physiotherapy for IBP is straightforward, inexpensive and quick. It appears that IBP is more prevalent in young adults than overall population data suggest so that targeting this population may be efficient. IBP questionnaires could be administered routinely during a physiotherapy assessment. HLA-B27 testing in this group of patients with IBP is a suitable screening tool. The sacroiliac joint changes identified were mild and their prognostic significance is not yet clear so that the value of early screening needs further evaluation. Disclosure statement: C.H. received research funding for this study from Abbott. A.K. received research funding for this study, and speaker and consultancy fees, from Abbott. All other authors have declared no conflicts of interes

Antigen presentation by MHC class I and CD1 molecules

Antigen presentation is the "sine qua non" of the mammalian adaptive immune stem. The assembly of MHC class 1/peptide complexes in the endoplasmic reticulum (ER) relies on the orchestrated interplay between different chaperonins, which assist MHC class I folding, and the peptide loading complex (PLC). Mutant lymphoblastoid cell lines with defective MHC class I surface expression have greatly helped the functional analysis of the PLC. The TAP transporter associated with antigen processing translocates MHC class I peptide ligands from the cytoso into the ER and is critical for successful MHC class I assembly and maturation. In the first two results chapters of this thesis I will describe the identification, clinical description and molecular and genetic analysis of a new clinical syndrome in a group of patients with dramatically reduced MHC class I surface expression. The disease in these patients could be identified as primary TAP-deficiency. The focus of the third and fourth chapter of this thesis lies on lipid antigen presentation via CDl molecules, which are known to present mycobacterial lipids to T lymphocytes. The first objective of this thesis was to generate recombinant mycobacterial lipid loaded CUl molecules as tools to measure mycobacterial lipid speclfic T cell responses in the TAP-deficient patients.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Valpha24-JalphaQ-independent, CD1d-restricted recognition of alpha-galactosylceramide by human CD4(+) and CD8alphabeta(+) T lymphocytes

Human CD1d molecules present an unknown ligand, mimicked by the synthetic glycosphingolipid -galactosylceramide (GC), to a highly conserved NKT cell subset expressing an invariant TCR V24-JQ paired with V11 chain (V24+V11+ invariant NK T cell (NKTinv)). The developmental pathway of V24+V11+NKTinv is still unclear, but recent studies in mice were consistent with a TCR instructive, rather than a stochastic, model of differentiation. Using CD1d-GC-tetramers, we demonstrate that in humans, TCR variable domains other than V24 and V11 can mediate specific recognition of CD1d-GC. In contrast to V24+V11+NKTinv cells, V24-/CD1d-GC-specific T cells express either CD8 or CD4 molecules, but they are never CD4 CD8 double negative. We show that CD8+V24-/CD1d-GC-specific T cells exhibit CD8-dependent specific cytotoxicity and have lower affinity TCRs than V24+/CD1d-GC-specific T cells. In conclusion, our results demonstrate that, contrary to the currently held view, recognition of CD1d-GC complex in humans is not uniformly restricted to the V24-JQ/V11 NKT cell subset, but can be mediated by a diverse range of V and V domains. The existence of a diverse repertoire of CD1d-GC-specific T cells in humans strongly supports their Ag-driven selection. <br/