Nucleobase adducts bind MR1 and stimulate MR1-restricted T cells

MR1T cells are a recently found class of T cells that recognize antigens presented by the major histocompatibility complex-I-related molecule MR1 in the absence of microbial infection. The nature of the self-antigens that stimulate MR1T cells remains unclear, hampering our understanding of their physiological role and therapeutic potential. By combining genetic, pharmacological, and biochemical approaches, we found that carbonyl stress and changes in nucleobase metabolism in target cells promote MR1T cell activation. Stimulatory compounds formed by carbonyl adducts of nucleobases were detected within MR1 molecules produced by tumor cells, and their abundance and antigenicity were enhanced by drugs that induce carbonyl accumulation. Our data reveal carbonyl-nucleobase adducts as MR1T cell antigens. Recognizing cells under carbonyl stress allows MR1T cells to monitor cellular metabolic changes with physiological and therapeutic implications.

Surface protein and functional analyses identify CD4+CD39+ TCR αβ+ and activated TCR Vδ1+ cells with distinct pro-inflammatory functions in Crohn's disease lesions

Crohn's disease (CD) is a chronic immune-mediated disorder of the gastrointestinal tract. Extensive screening studies have revealed the accumulation of immune cell subsets with unique plasticity and immunoregulatory properties in patients with CD. We performed phenotypic and functional studies on inflamed and non-inflamed bioptic tissue to investigate the presence of distinct T cells in the intestinal mucosa of CD patients. We analysed hundreds of surface molecules expressed on cells isolated from the intestinal tissue of CD patients using anti-CD45 mAbs-based barcoding. A gene ontology enrichment analysis showed that proteins that regulate the activation of T cells were the most enriched group. We, therefore, designed T-cell focused multicolour flow-cytometry panels and performed clustering analysis which revealed an accumulation of activated TEM CD4+CD39+ T cells producing IL-17 and IL-21 and increased frequency of terminally differentiated TCR Vδ1+ cells producing TNF-α and IFN-γ in inflamed tissue of CD patients. The different functional capacities of CD4+ and TCR Vδ1+ cells in CD lesions indicate their non-overlapping contribution to inflammation. The abnormally high number of terminally differentiated TCR Vδ1+ cells suggests that they are continuously activated in inflamed tissue, making them a potential target for novel therapies.

Five-year recurrence after endoscopic approach to pilonidal sinus disease: A multicentre experience

PURPOSE

The aim of this study was to evaluate the 5-year recurrence rate of pilonidal sinus disease (PSD) after endoscopic sinusectomy and identify risk factors for recurrence.

METHODS

All consecutive patients from September 2011 through December 2017 who underwent endoscopic sinusectomy at seven referral centres for pilonidal sinus treatment were retrospectively analysed from a prospectively maintained database.

RESULTS

Out of 290 patients (185 males versus 105 female, with a mean age of 25.5±6.9), 73 presented recurrence at 5-year follow-up with a recurrence rate of 25.2%. The number of pilonidal sinus with pits off the midline (p = 0.001) and the mean (SD) distance from the most lateral orifice to the midline (p = 0.001) were higher in the group of patients with recurrence at 5-year follow-up. Multivariate analysis demonstrated that the position of the pits off the midline (p = 0.001) and the distance of the most lateral orifice from the midline (p = 0.001) were independent risk factors for recurrence at 5-year follow-up. Receiver operating characteristic (ROC) curve analysis showed that the distance of lateral orifice from midline predicted an 82.2% possibility of recurrence at 5-year follow-up and Youden's test identified the best cut-off as 2 cm for this variable. Out of 195 cases with the most lateral orifice less than 2 cm from the midline, 13 presented recurrence at 5-year follow-up with a recurrence rate of 6.7%. Out of 95 cases with the most lateral orifice more than 2 cm from midline, 60 showed recurrence at 5-year follow-up with a recurrence rate of 63.2%.

CONCLUSIONS

This data may help guide which disease characteristics predict the optimal use of an endoscopic pilonidal sinus technique.

Promiscuous recognition of MR1 drives self-reactive mucosal-associated invariant T cell responses

Mucosal-associated invariant T (MAIT) cells use canonical semi-invariant T cell receptors (TCR) to recognize microbial riboflavin precursors displayed by the antigen-presenting molecule MR1. The extent of MAIT TCR crossreactivity toward physiological, microbially unrelated antigens remains underexplored. We describe MAIT TCRs endowed with MR1-dependent reactivity to tumor and healthy cells in the absence of microbial metabolites. MAIT cells bearing TCRs crossreactive toward self are rare but commonly found within healthy donors and display T-helper-like functions in vitro. Experiments with MR1-tetramers loaded with distinct ligands revealed significant crossreactivity among MAIT TCRs both ex vivo and upon in vitro expansion. A canonical MAIT TCR was selected on the basis of extremely promiscuous MR1 recognition. Structural and molecular dynamic analyses associated promiscuity to unique TCRβ-chain features that were enriched within self-reactive MAIT cells of healthy individuals. Thus, self-reactive recognition of MR1 represents a functionally relevant indication of MAIT TCR crossreactivity, suggesting a potentially broader role of MAIT cells in immune homeostasis and diseases, beyond microbial immunosurveillance.

Human T cells engineered with a leukemia lipid-specific TCR enables donor-unrestricted recognition of CD1c-expressing leukemia

Acute leukemia relapsing after chemotherapy plus allogeneic hematopoietic stem cell transplantation can be treated with donor-derived T cells, but this is hampered by the need for donor/recipient MHC-matching and often results in graft-versus-host disease, prompting the search for new donor-unrestricted strategies targeting malignant cells. Leukemia blasts express CD1c antigen-presenting molecules, which are identical in all individuals and expressed only by mature leukocytes, and are recognized by T cell clones specific for the CD1c-restricted leukemia-associated methyl-lysophosphatidic acid (mLPA) lipid antigen. Here, we show that human T cells engineered to express an mLPA-specific TCR, target diverse CD1c-expressing leukemia blasts in vitro and significantly delay the progression of three models of leukemia xenograft in NSG mice, an effect that is boosted by mLPA-cellular immunization. These results highlight a strategy to redirect T cells against leukemia via transfer of a lipid-specific TCR that could be used across MHC barriers with reduced risk of graft-versus-host disease.

Leukaemia therapy may benefit from the use of antigens that are less restricted to individual donors. Here the authors engineered T cells with a TCR specific for a CD1c restricted lipid leukaemia antigen and show that they can protect against disease progression in mouse leukaemia xenograft models.

Clinical and dermoscopic changes of acquired melanocytic nevi of patients treated with afamelanotide

BACKGROUND

Afamelanotide (AFA) is a synthetic analogue of α-melanocyte-stimulating hormone that is approved for the treatment of patients affected by erythropoietic protoporphyria (EPP). AFA induces a "sun free" tanning and changes of acquired melanocytic nevi (AMN) that are generically described as "darkening".

OBJECTIVES

To assess clinical and dermoscopic AMN changes during AFA treatment.

METHODS

Adult EPP patients treated with two AFA implants 50 days apart were enrolled. They underwent a clinical and dermoscopic examination of all AMN at baseline (T0), and after 5 (T1) and 12 (T2) months from the first AFA implant. The general pattern, symmetry, number, and size of pigmented globules, morphology of the pigment network, and dermoscopic melanoma features were assessed.

RESULTS

Fifteen patients were enrolled with 103 AMN. At T1 all reticular and 2-component AMN showed a focal network thickening that returned to baseline by T2. The increase of globules' number was observed at T1 but not at T2. The difference in number was not influenced by patients' age or phototype. Dermoscopic changes suggestive of malignancy were never seen. The development of new AMN was never registered.

CONCLUSIONS

AFA treatment induces reversible changes of AMN dermoscopic morphology without findings suggestive of malignant transformation and it does not stimulate the development of new AMN.

Antigen specificities and functional properties of MR1-restricted T cells

MR1 is an MHC class I-like molecule with unique structural and biological features that make it an important member among the molecules involved in antigen presentation to T cells. Distinctive features include ubiquitous expression of the MR1 gene and its monomorphism. Another relevant property is that the MR1 protein appears at very low levels on the plasma membrane and its surface expression is regulated by antigen binding. Finally, the nature of presented antigens differs from those that bind other presenting molecules and includes small metabolites of microbial and self-origin, small drugs and tumor-associated antigens. This opinion paper describes in detail some of those features and discusses recent literature in the field.

MR1-Restricted T Cells Are Unprecedented Cancer Fighters

Non-polymorphic MHC class I-related molecule MR1 presents antigenic bacterial metabolites to mucosal-associated invariant T (MAIT) cells and self-antigens to MR1-restricted T (MR1T) cells. Both MR1-restricted T cell populations are readily identified in healthy individuals, with MAIT cells accounting for 1-10% of circulating T cells, while MR1T cells have frequencies comparable to peptide-specific T cells (<0.1%). Self-reactive MR1T cells display a heterogeneous phenotype, and are capable of releasing both T_H1 and T_H2 cytokines, supporting not only activation of inflammation but also contributing to its regulation. Importantly, MR1T cells recognize and kill a diverse range of MR1-expressing tumor cells. On the other hand, evidence suggests MAIT cells augment cancer growth and metastases. This review addresses the potential role of MR1-restricted T cells in controlling tumor cells, facilitating their elimination and regulating cancer immunity. We also discuss therapeutic opportunities surrounding MR1-restricted T cells in cancer.

Isolation and Characterization of MAIT Cells from Human Tissue Biopsies

Human mucosal-associated invariant T (MAIT) cells are unconventional T cells highly enriched in tissues exposed to microbial antigens including the oral, gastrointestinal and genital mucosae, liver, and lung. Here we describe a protocol for isolation and characterization of peripheral blood and tissue-infiltrating MAIT cells by using multicolor flow cytometry. This technology allows the analysis of multiple markers in a single sample at a single-cell level. Study of human samples requires particular care since the sample amount is often limited. We present a protocol optimized for the isolation and characterization of human MAIT cells and the identification of MAIT cell populations detected by simultaneous expression of multiple activation markers and inhibitory receptors.

Generation of induced Pluripotent Stem Cells (UNIBSi008-A, UNIBSi008-B, UNIBSi008-C) from an Ataxia-Telangiectasia (AT) patient carrying a novel homozygous deletion in ATM gene

Using a Sendai Virus based vector delivering Yamanaka Factors, we generated induced Pluripotent Stem Cells (iPSCs) from peripheral blood mononuclear cells of a patient affected by Ataxia Telangiectasia (AT), caused by a novel homozygous deletion in ATM, spanning exons 5-7. Three clones were fully characterized for pluripotency and capability to differentiate. These clones preserved the causative mutation of parental cells and genomic stability over time (>100 passages). Furthermore, in AT derived iPSCs we confirmed the impaired DNA damage response after ionizing radiation. All these data underline potential usefulness of our clones as in vitro AT disease model.

Treadmill training in patients affected by Charcot-Marie-Tooth neuropathy: results of a multicenter, prospective, randomized, single-blind, controlled study

Background and purpose

Muscle‐strengthening, stretching or proprioceptive treatments may slow symptom progression in Charcot—Marie–Tooth (CMT) neuropathy. The aim of the study was to evaluate safety and efficacy of treadmill training in CMT1A.

Methods

We planned a multicenter, prospective, randomized, single‐blind, controlled study. We recruited 53 outpatients affected by CMT1A and randomized them into two treatment groups: one underwent stretching and proprioceptive exercise, whereas the other was additionally treated with treadmill training (TreSPE). Primary outcome measures (OMs) were the walking evaluations and secondary OM was the balance assessment. All participants were assessed at baseline and after 3 and 6 months of treatment.

Results

Most patients showed an improvement in at least one OM after 3 months [42/47 (89.4%)] and 6 months [38/40 (95%)] of treatment. No adverse events were reported in either group.

Conclusions

The most important finding was that both stretching and proprioceptive exercise and treadmill training had an objective benefit on patients affected by CMT disease, without causing overwork weakness. We had a low rate of drop out and did not find deterioration in motor performance. Our results also confirm that applying evidence‐based medicine methods to rehabilitative research is the correct way to test the efficacy of a treatment.

Unique T-Cell Populations Define Immune-Inflamed Hepatocellular Carcinoma

BACKGROUND & AIMS

The characterization of T cells infiltrating hepatocellular carcinoma (HCC) provides information on cancer immunity and also on selection of patients with precise indication of immunotherapy. The aim of the study was to characterize T-cell populations within tumor tissue and compare them with non-neoplastic liver tissue as well as circulating cells of the same patients.

METHODS

The presence of unique cell populations was investigated in 36 HCC patients by multidimensional flow cytometry followed by t-distributed stochastic neighbor embedding analysis. Functional activity of tumor-infiltrating T cells was determined after activation by phorbol 12-myristate 13-acetate and ionomycin.

RESULTS

Within the tumor there were more cells expressing CD137 and ICOS than in non-neoplastic liver tissue, possibly after recent antigenic activation. These cells contained several populations, including the following: (1) functionally impaired, proliferating CD4⁺ cells co-expressing Inducible T-cell costimulator (ICOS) and T cell immunoreceptor with Ig and ITIM domains (TIGIT); (2) functionally active CD8⁺ cells co-expressing CD38 and Programmed cell-death protein 1 (PD1); and (3) CD4-CD8 double-negative T-cell receptor αβ and γδ cells (both non-major histocompatibility complex-restricted T cells). When the identified clusters were compared with histologic classification performed on the same samples, an accumulation of activated T cells was observed in immune-inflamed HCC. The same analyses performed in 7 patients receiving nivolumab treatment showed a remarkable reduction in the functionally impaired CD4⁺ cells, which returned to almost normal activity over time.

CONCLUSIONS

Unique populations of activated T cells are present in HCC tissue, whose antigen specificity remains to be investigated. Some of these cell populations are functionally impaired and nivolumab treatment restores their responsiveness. The finding of ongoing immune response within the tumor shows which lymphocyte populations are impaired within the HCC and identifies the patients who might take benefit from immunotherapy.

Hand Rehabilitation Treatment for Charcot-Marie-Tooth Disease: An Open Label Pilot Study

Objective

Charcot-Marie-Tooth neuropathy affects mainly and early the lower limbs, but hands deformities are a relevant problem, which involves the quality of life of the patients. Unfortunately, there are few studies about the evaluation of the upper limbs and very rare works about the rehabilitation. A treatment study at the moment is missing and it is important to search rehabilitation exercises to improve the dexterity and the quality of life of the patients.

Methods

We recruited 9 patients with clinical and genetic diagnosis of CMT and we proposed a rehabilitation protocol which includes muscle recruitment, stretching and proprioceptive exercises for the hand with the duration of 4 weeks (two sessions for week). We evaluated the patients before and one week after the treatment with Thumb Opposition Test, Sollerman Hand Function Scale, dynamometry (tripod pinch and hand grip).

Results

The rehabilitation protocol has been well tolerated and there were not dropouts. We did not observe any worsening in every scale we used. Every parameter tested showed an improvement especially in the right/dominant hand.

Conclusion

This study demonstrates that this three phases treatment is well tolerated by patients, it is not detrimental for the hands status and perfectly reproducible by professionals. Moreover, this could be the basis for future randomized single blind projects.

The Conventional Nature of Non-MHC-Restricted T Cells

The definition “unconventional T cells” identifies T lymphocytes that recognize non-peptide antigens presented by monomorphic antigen-presenting molecules. Two cell populations recognize lipid antigens and small metabolites presented by CD1 and MR1 molecules, respectively. A third cell population expressing the TCR Vγ9Vδ2 is stimulated by small phosphorylated metabolites. In the recent past, we have learnt a lot about the selection, tissue distribution, gene transcription programs, mode of expansion after antigen recognition, and persistence of these cells. These studies depict their functions in immune homeostasis and diseases. Current investigations are revealing that unconventional T cells include distinct sub-populations, which display unexpected similarities to classical MHC-restricted T cells in terms of TCR repertoire diversity, antigen specificity variety, functional heterogeneity, and naïve-to-memory differentiation dynamic. This review discusses the latest findings with a particular emphasis on these T cells, which appear to be more conventional than previously appreciated, and with the perspective of using CD1 and MR1-restricted T cells in vaccination and immunotherapy.

Contact sensitizers trigger human CD1-autoreactive T-cell responses

Allergic contact dermatitis is a primarily T-cell-mediated inflammatory skin disease induced by exposure to small molecular-weight haptens, which covalently bind to proteins. The abundance of cutaneous T cells that recognize CD1a antigen-presenting molecules raises the possibility that MHC-independent antigen presentation may be relevant in some hapten-driven immune responses. Here we examine the ability of contact sensitizers to influence CD1-restricted immunity. Exposure of human antigen-presenting cells such as monocyte-derived dendritic cells and THP-1 cells to the prototypical contact sensitizer dinitrochlorobenzene potentiated the response of CD1a- and CD1d-autoreactive T cells, which released a vast array of cytokines in a CD1- and TCR-dependent manner. The potentiating effects of dinitrochlorobenzene depended upon newly synthesized CD1 molecules and the presence of endogenous stimulatory lipids. Further examination of a broad panel of contact sensitizers revealed 1,4-benzoquinone, resorcinol, isoeugenol, and cinnamaldehyde to activate the same type of CD1-restricted responses. These findings provide a basis for the antigen-specific activation of skin-associated CD1-restricted T cells by small molecules and may have implications for contact sensitizer-induced inflammatory skin diseases.

Functionally diverse human T cells recognize non-microbial antigens presented by MR1

MHC class I-related molecule MR1 presents riboflavin- and folate-related metabolites to mucosal-associated invariant T cells, but it is unknown whether MR1 can present alternative antigens to other T cell lineages. In healthy individuals we identified MR1-restricted T cells (named MR1T cells) displaying diverse TCRs and reacting to MR1-expressing cells in the absence of microbial ligands. Analysis of MR1T cell clones revealed specificity for distinct cell-derived antigens and alternative transcriptional strategies for metabolic programming, cell cycle control and functional polarization following antigen stimulation. Phenotypic and functional characterization of MR1T cell clones showed multiple chemokine receptor expression profiles and secretion of diverse effector molecules, suggesting functional heterogeneity. Accordingly, MR1T cells exhibited distinct T helper-like capacities upon MR1-dependent recognition of target cells expressing physiological levels of surface MR1. These data extend the role of MR1 beyond microbial antigen presentation and indicate MR1T cells are a normal part of the human T cell repertoire.

DOI:http://dx.doi.org/10.7554/eLife.24476.001

White blood cells called T cells recognize germs and infected cells, and get rid of other cells in the body that look different to healthy cells – for example, tumor cells. These activities all depend on a molecule called the T cell receptor (or TCR for short), which is found on the surface of the T cells. Each TCR interacts with a specific complex on the surface of the target cell. One of the molecules recognized by the TCR is known as MHC class I-related (shortened to MR1). This molecule attracts TCRs to infected cells, but it was not know if the MR1 molecule could attract TCRs to cancer cells too.

Lepore et al. now show that there are indeed T cells in humans that recognize cancer cells through interaction with the MR1 molecules produced by the cancer cells. This new group of T cells has been named MR1T, and the cells can be easily detected in the blood of healthy individuals. The cells can be classified as a new cell population based on their capacity to recognize MR1 and how they react with different types of cancer cells.

Importantly, the MR1 that attracts these TCRs is the same in all people, and so the same TCR may recognize MR1-expressing cancer cells from different patients. The next challenge is to identify MR1T cells that recognize and kill cancer cells from different tissues. These studies will hopefully pave the way for new and broader strategies to combat cancer.

DOI:http://dx.doi.org/10.7554/eLife.24476.002

The Immunology of CD1- and MR1-Restricted T Cells

CD1- and MHC-related molecule-1 (MR1)-restricted T lymphocytes recognize nonpeptidic antigens, such as lipids and small metabolites, and account for a major fraction of circulating and tissue-resident T cells. They represent a readily activated, long-lasting population of effector cells and contribute to the early phases of immune response, orchestrating the function of other cells. This review addresses the main aspects of their immunological functions, including antigen and T cell receptor repertoires, mechanisms of nonpeptidic antigen presentation, and the current evidence for their participation in human and experimental diseases.

Hemopoietic cell kinase (Hck) and p21-activated kinase 2 (PAK2) are involved in the down-regulation of CD1a lipid antigen presentation by HIV-1 Nef in dendritic cells

Dendritic cells (DCs) play a major role in in vivo pathogenesis of HIV-1 infection. Therefore, DCs may provide a promising strategy to control and eventually overcome the fatal infection. Especially, immature DCs express all CD1s, the non-MHC lipid antigen -presenting molecules, and HIV-1 Nef down-regulates CD1 expression besides MHC. Moreover, CD1d-restricted CD4(+) NKT cells are infected by HIV-1, reducing the number of these cells in HIV-1-infected individuals. To understand the exact role of DCs and CD1-mediated immune response during HIV-1 infection, Nef down-regulation of CD1a-restricted lipid/glycolipid Ag presentation in iDCs was analyzed. We demonstrated the involvement of the association of Nef with hemopoietic cell kinase (Hck) and p21-activated kinase 2 (PAK2), and that Hck, which is expressed strongly in iDCs, augmented this mutual interaction. Hck might be another therapeutic target to preserve the function of HIV-1 infected DCs, which are potential reservoirs of HIV-1 even after antiretroviral therapy.

Globotriaosylceramide inhibits iNKT-cell activation in a CD1d-dependent manner

Globotriaosylceramide (Gb3) is a glycosphingolipid present in cellular membranes that progressively accumulates in Fabry disease. Invariant Natural Killer T (iNKT) cells are a population of lipid-specific T cells that are phenotypically and functionally altered in Fabry disease. The mechanisms responsible for the iNKT-cell alterations in Fabry disease are not well understood. Here, we analyzed the effect of Gb3 on CD1d-mediated iNKT-cell activation in vitro using human cells and in vivo in the mouse model. We found that Gb3 competes with endogenous and exogenous antigens for CD1d binding, thereby reducing the activation of iNKT cells. This effect was exerted by a reduction in the amount of stimulatory CD1d:α-GalCer complexes in the presence of Gb3 as demonstrated by using an mAb specific for the complex. We also found that administration of Gb3 delivered to the same APC as α-GalCer, induces reduced iNKT-cell activation in vivo. This work highlights the complexity of iNKT-cell activation and the importance of nonantigenic glycosphingolipids in the modulation of this process.

Tinetti and Berg balance scales correlate with disability in hereditary peripheral neuropathies: a preliminary study

BACKGROUND

The combination of distal muscle weakness, sensory defects and feet deformities leads to disequilibrium in patients affected by Charcot-Marie-Tooth (CMT) neuropathy. Studies relating the outcome of balance scales and clinical severity of CMT are lacking.

AIM

To evaluate the accuracy of the Tinetti Balance scale (TBS) and Berg Balance scale (BBS) in identifying balance disorders and quantifying disease severity in CMT patients.

DESIGN

Observational study.

SETTING

University of Genoa-IRCCS AOU San Martino IST-Department of Neurology, Italy.

POPULATION

Nineteen individuals with a diagnosis of CMT (12 females, 7 males, age 41.26±12.42).

METHODS

All subjects underwent an evaluation with both TBS and BBS. Disability was quantified with CMT neuropathy score (CMTNS). Moreover, a complete neurophysiological study was performed. Distal lower limbs strength was evaluated with MRC scale. Pearson rank order correlation was used to determine the correlation between the scores on the two tests and to identify an eventual correlation between TBS or BBS and the CMTNS.

RESULTS

Both scales showed a highly significant negative correlation with the CMTNS (r=-0.78, P<0.0005 and r=-0.77, P<0.001, respectively) and distal weakness on the anterior tibial muscles (AT) (TBS: AT left: r=0.65, P<0.005 and AT right: 0.59, P<0.01; BBS: AT left r=+0.71, P<0.001 and AT right r=+0.66, P<0.005). We found also a highly significant, positive correlation between the two different balance scales (r=+0.9, P<0.0001).

CONCLUSION

TBS and BBS strongly correlate with disease disability and distal muscular weakness.

CLINICAL REHABILITATION IMPACT

Both TBS and BBS may play a relevant role in the assessment of disability in patients affected by CMT. Further studies are needed to validate our results in a larger population.

Phosphoantigen Presentation to TCR γδ Cells, a Conundrum Getting Less Gray Zones

The mechanistic requirements of antigen recognition by T cells expressing a γδ TCR has revealed important differences with those of αβ TCR cells and, despite impressive new data generated in the very recent years, they remain poorly understood. Based on the structure of the TCR chains and the tissue distribution, γδ cells are represented in a variety of populations. The major subset of human peripheral blood γδ cells express Vγ9Vδ2 TCR heterodimers and are all stimulated by phosphorylated metabolites (commonly called phosphoantigens). Phosphoantigens are molecules with a very small mass and only stimulate Vγ9Vδ2 cells in the presence of antigen-presenting cells, suggesting a strict requirement for dedicated antigen-presenting molecules. Recent studies have identified butyrophilin (BTN) 3A1 as the molecule necessary to stimulate Vγ9Vδ2 cells. BTN3A1 extracellular, transmembrane, and cytoplasmic domains have different functions, including cognate interaction with the Vγ9Vδ2 TCR, binding of the phosphoantigens, and interaction with cytoplasmic proteins. This review mainly discusses the known molecular mechanisms of BTN3A1-mediated antigen presentation to γδ cells and proposes a model of phosphoantigen presentation, which integrates past and recent studies.

Targeting leukemia by CD1c-restricted T cells specific for a novel lipid antigen

A subset of CD1c-restricted T lymphocytes exhibits strong reactivity against leukemia cells. These T cells recognize methyl-lysophosphatidic acid (mLPA), a novel lipid antigen produced by acute leukemia cells. Considering that CD1c-restricted T cells display efficacious anti-leukemia activities in a mouse model, this lipid antigen thus represents a novel target in the immunotherapy of hematological malignancies.

Nonclassical T cells and their antigens in tuberculosis

T cells that recognize nonpeptidic antigens, and thereby are identified as nonclassical, represent important yet poorly characterized effectors of the immune response. They are present in large numbers in circulating blood and tissues and are as abundant as T cells recognizing peptide antigens. Nonclassical T cells exert multiple functions including immunoregulation, tumor control, and protection against infections. They recognize complexes of nonpeptidic antigens such as lipid and glycolipid molecules, vitamin B2 precursors, and phosphorylated metabolites of the mevalonate pathway. Each of these antigens is presented by antigen-presenting molecules other than major histocompatibility complex (MHC), including CD1, MHC class I-related molecule 1 (MR1), and butyrophilin 3A1 (BTN3A1) molecules. Here, we discuss how nonclassical T cells participate in the recognition of mycobacterial antigens and in the mycobacterial-specific immune response.

A novel self-lipid antigen targets human T cells against CD1c(+) leukemias

T cells that recognize self-lipids presented by CD1c are frequent in the peripheral blood of healthy individuals and kill transformed hematopoietic cells, but little is known about their antigen specificity and potential antileukemia effects. We report that CD1c self-reactive T cells recognize a novel class of self-lipids, identified as methyl-lysophosphatidic acids (mLPAs), which are accumulated in leukemia cells. Primary acute myeloid and B cell acute leukemia blasts express CD1 molecules. mLPA-specific T cells efficiently kill CD1c(+) acute leukemia cells, poorly recognize nontransformed CD1c-expressing cells, and protect immunodeficient mice against CD1c(+) human leukemia cells. The identification of immunogenic self-lipid antigens accumulated in leukemia cells and the observed leukemia control by lipid-specific T cells in vivo provide a new conceptual framework for leukemia immune surveillance and possible immunotherapy.

The T-Cell Response to Lipid Antigens of Mycobacterium tuberculosis

T-cells recognize lipid antigens presented by dedicated antigen-presenting molecules that belong to the CD1 family. This review discusses the structural properties of CD1 molecules, the nature of mycobacterial lipid antigens, and the phenotypic and functional properties of T-cells recognizing mycobacterial lipids. In humans, the five CD1 genes encode structurally similar glycoproteins that recycle in and thus survey different cellular endosomal compartments. The structure of the CD1-lipid-binding pockets, their mode of intracellular recycling and the type of CD1-expressing antigen-presenting cells all contribute to diversify lipid immunogenicity and presentation to T-cells. Mycobacteria produce a large variety of lipids, which form stable complexes with CD1 molecules and stimulate specific T-cells. The structures of antigenic lipids may be greatly different from each other and each lipid may induce unique T-cells capable of discriminating small lipid structural changes. The important functions of some lipid antigens within mycobacterial cells prevent the generation of negative mutants capable of escaping this type of immune response. T-cells specific for lipid antigens are stimulated in tuberculosis and exert protective functions. The mechanisms of antigen recognition, the type of effector functions and the mode of lipid-specific T-cell priming are discussed, emphasizing recent evidence of the roles of lipid-specific T-cells in tuberculosis.

Professional differences in antigen presentation to iNKT cells

Invariant natural killer T cells are preactivated lymphocytes that react upon recognition of CD1d-antigen complexes. Accordingly, any type of CD1d-positive cell could behave as antigen-presenting cell (APC). In this issue of Immunity, Arora et al. (2014), report that professional APCs still make the difference.

Butyrophilin 3A1 binds phosphorylated antigens and stimulates human γδ T cells

Human T cells that express a T cell antigen receptor (TCR) containing γ-chain variable region 9 and δ-chain variable region 2 (Vγ9Vδ2) recognize phosphorylated prenyl metabolites as antigens in the presence of antigen-presenting cells but independently of major histocompatibility complex (MHC), the MHC class I-related molecule MR1 and antigen-presenting CD1 molecules. Here we used genetic approaches to identify the molecule that binds and presents phosphorylated antigens. We found that the butyrophilin BTN3A1 bound phosphorylated antigens with low affinity, at a stoichiometry of 1:1, and stimulated mouse T cells with transgenic expression of a human Vγ9Vδ2 TCR. The structures of the BTN3A1 distal domain in complex with host- or microbe-derived phosphorylated antigens had an immunoglobulin-like fold in which the antigens bound in a shallow pocket. Soluble Vγ9Vδ2 TCR interacted specifically with BTN3A1-antigen complexes. Accordingly, BTN3A1 represents an antigen-presenting molecule required for the activation of Vγ9Vδ2 T cells.

Deciphering the role of CD1e protein in mycobacterial phosphatidyl-myo-inositol mannosides (PIM) processing for presentation by CD1b to T lymphocytes

Lipids are important antigens that induce T cell-mediated specific immune responses. They are presented to T lymphocytes by a specific class of MHC-I like proteins, termed CD1. The majority of the described CD1-presented mycobacterial antigens are presented by the CD1b isoform. We previously demonstrated that the stimulation of CD1b-restricted T cells by the hexamannosylated phosphatidyl-myo-inositol (PIM(6)), a family of mycobacterial antigens, requires a prior partial digestion of the antigen oligomannoside moiety by α-mannosidase and that CD1e is an accessory protein absolutely required for the generation of the lipid immunogenic form. Here, we show that CD1e behaves as a lipid transfer protein influencing lipid immunoediting and membrane transfer of PIM lipids. CD1e selectively assists the α-mannosidase-dependent digestion of PIM(6) species according to their degree of acylation. Moreover, CD1e transfers only diacylated PIM from donor to acceptor liposomes and also from membranes to CD1b. This study provides new insight into the molecular mechanisms by which CD1e contributes to lipid immunoediting and CD1-restricted presentation to T cells.

Peroxisome-derived lipids are self antigens that stimulate invariant natural killer T cells in the thymus

The development and maturation of semi-invariant natural killer T cells (iNKT cells) rely on the recognition of self antigens presented by CD1d restriction molecules in thymus. The nature of the stimulatory thymic self lipids remains elusive. We isolated lipids from thymocytes and found that ether-bonded mono-alkyl glycerophosphates and the precursors and degradation products of plasmalogens stimulated iNKT cells. Synthetic analogs showed high potency in activating thymic and peripheral iNKT cells. Mice deficient in the peroxisomal enzyme glyceronephosphate O-acyltransferase (GNPAT), essential for the synthesis of ether lipids, had significant alteration of the thymic maturation of iNKT cells and fewer iNKT cells in both thymus and peripheral organs, which confirmed the role of ether-bonded lipids as iNKT cell antigens. Thus, peroxisome-derived lipids are nonredundant self antigens required for the generation of a full iNKT cell repertoire.

Novel insights into lipid antigen presentation

T cells recognizing lipid antigens are present in large numbers in circulating blood. They exert multiple functions including immunoregulation, tumour surveillance and protection during infection. Here, we review the latest information on the mechanisms of lipid antigen presentation by CD1 molecules. Recent studies have provided insight into CD1 trafficking within the cell, lipid distribution and handling, CD1 maturation, lipid antigen processing and loading. The structural resolution of all human CD1 molecules has revealed unique features that correlate with function. Molecular mechanisms regulating CD1 expression and multiple evasion mechanisms evolved by viral and bacterial pathogens have been disclosed. With rapid progression, these studies have decoded lipid-specific immunity and have revealed the important immunological role of this type of antigen recognition.

A novel menin gene deletional mutation in a little series of Italian patients affected by apparently sporadic multiple endocrine neoplasia type 1 syndrome

AIM

To perform a genetic screening for the multiple endocrine neoplasia type 1 (MEN1) gene mutations in patients affected by an apparently sporadic form of the disease, referred to an internal medicine unit of a large general hospital.

SUBJECTS AND METHODS

In a group of 12 consecutive patients presenting clinical features of MEN type 1 syndrome, we performed a genetic screening for germline MEN1 gene mutations, including complete sequencing of the coding region (exons 2 to 10) and multiplex ligation-dependent probe amplification analysis for large deletion detection.

RESULTS

Among these patients affected by apparently sporadic MEN type 1 syndrome, a targeted clinical history could detect indirect support for a diagnosis of familial condition only in 2 cases. The genetic screening identified pathogenic germline MEN1 gene mutations in 3 patients (25%). A previously unknown 18 base-pair deletion within exon 3, c.564_581delCAATGGGGAGCAGACAGC, resulting in loss of 6 amino acids (pAsp189_Ala194del), was found in heterozygosis in a woman affected by primary hyperparathyroidism and multifocal pancreatic neoplasia.

CONCLUSIONS

Our results underscore the importance of performing genetic testing also in apparently sporadic MEN1 patients and extend the list of molecular variants leading to inactivation of the MEN1 gene.