CD1a Proteins Research Articles

Impaired intratumoral dendritic cell function and potential predictive value of dendritic cell markers for metastasis in malignant salivary gland tumors.

The differentiation between primary and metastatic salivary gland neoplasms (SGNs) helps in determining appropriate management strategies, including the need for additional diagnostic tests, surveillance, or aggressive treatment. The purpose of this study was to identify and quantify the immature and mature dendritic cells (DCs) in metastatic and no metastatic SGNs and determine its association with clinicopathological findings. Cross-sectional, observational, and descriptive study that includes 33 malignant salivary gland neoplasms [MSGN (6, 18.1% metastatic)], and 22 pleomorphic adenomas (PA), as a control group. Clinical and histopathological characteristics were obtained. Immunohistochemistry for human leukocyte antigen D-related (HLA-DR), CD1a, CD83, and Ki-67 proteins was done. Positive intra- and peritumoral DCs were counted. Individuals with MSGN had a lower density of intratumoral HLA-DR+ cells than those with PA (p=0.001), Ki-67 immunostaining was significantly higher in MSGN than in PA (6% vs. 1.4%, p<0.001). Metastatic MSGN showed less intratumoral CD1a+ than non-metastatic (3.2 vs. 165.1, p=0.001). No differences in intra- and peritumoral CD83+ cells were found between benign and malignant SGN. These results suggest that the immune-protective function of intratumoral DCs is compromised in MSGNs. DCs markers may represent useful prediction tools for metastases in salivary gland malignancies, with crucial implications in the implementation of appropriate disease management strategies.

CD1a and bound lipids drive T-cell responses in human skin disease.

In addition to serving as the main physical barrier with the outside world, human skin is abundantly infiltrated with resident αβ T cells that respond differently to self, infectious, microbiome, and noxious stimuli. To study skin T cells during infection and inflammation, experimental biologists track T-cell surface phenotypes and effector functions, which are often interpreted with the untested assumption that MHC proteins and peptide antigens drive measured responses. However, a broader perspective is that CD1 proteins also activate human T cells, and in skin, Langerhans cells (LCs) are abundant antigen presenting cells that express extremely high levels of CD1a. The emergence of new experimental tools, including CD1a tetramers carrying endogenous lipids, now show that CD1a-reactive T cells comprise a large population of resident T cells in human skin. Here, we review studies showing that skin-derived αβ T cells directly recognize CD1a proteins, and certain bound lipids, such as contact dermatitis allergens, trigger T-cell responses. Other natural skin lipids inhibit CD1a-mediated T-cell responses, providing an entry point for the development of therapeutic lipids that block T-cell responses. Increasing evidence points to a distinct role of CD1a in type 2 and 22 T-cell responses, providing new insights into psoriasis, contact dermatitis, and other T-cell-mediated skin diseases.

CD1a selectively captures endogenous cellular lipids that broadly block T cell response.

We optimized lipidomics methods to broadly detect endogenous lipids bound to cellular CD1a proteins. Whereas membrane phospholipids dominate in cells, CD1a preferentially captured sphingolipids, especially a C42, doubly unsaturated sphingomyelin (42:2 SM). The natural 42:2 SM but not the more common 34:1 SM blocked CD1a tetramer binding to T cells in all human subjects tested. Thus, cellular CD1a selectively captures a particular endogenous lipid that broadly blocks its binding to TCRs. Crystal structures show that the short cellular SMs stabilized a triad of surface residues to remain flush with CD1a, but the longer lipids forced the phosphocholine group to ride above the display platform to hinder TCR approach. Whereas nearly all models emphasize antigen-mediated T cell activation, we propose that the CD1a system has intrinsic autoreactivity and is negatively regulated by natural endogenous inhibitors selectively bound in its cleft. Further, the detailed chemical structures of natural blockers could guide future design of therapeutic blockers of CD1a response.

T Cells Specific for a Mycobacterial Glycolipid Expand after Intravenous Bacillus Calmette-Guérin Vaccination.

Intradermal vaccination with Mycobacterium bovis bacillus Calmette-Guérin (BCG) protects infants from disseminated tuberculosis, and i.v. BCG protects nonhuman primates (NHP) against pulmonary and extrapulmonary tuberculosis. In humans and NHP, protection is thought to be mediated by T cells, which typically recognize bacterial peptide Ags bound to MHC proteins. However, during vertebrate evolution, T cells acquired the capacity to recognize lipid Ags bound to CD1a, CD1b, and CD1c proteins expressed on APCs. It is unknown whether BCG induces T cell immunity to mycobacterial lipids and whether CD1-restricted T cells are resident in the lung. In this study, we developed and validated Macaca mulatta (Mamu) CD1b and CD1c tetramers to probe ex vivo phenotypes and functions of T cells specific for glucose monomycolate (GMM), an immunodominant mycobacterial lipid Ag. We discovered that CD1b and CD1c present GMM to T cells in both humans and NHP. We show that GMM-specific T cells are expanded in rhesus macaque blood 4 wk after i.v. BCG, which has been shown to protect NHP with near-sterilizing efficacy upon M. tuberculosis challenge. After vaccination, these T cells are detected at high frequency within bronchoalveolar fluid and express CD69 and CD103, markers associated with resident memory T cells. Thus, our data expand the repertoire of T cells known to be induced by whole cell mycobacterial vaccines, such as BCG, and show that lipid Ag-specific T cells are resident in the lungs, where they may contribute to protective immunity.

Human skin is colonized by T cells that recognize CD1a independently of lipid.

CD1a-autoreactive T cells contribute to skin disease, but the identity of immunodominant self-lipid antigens and their mode of recognition are not yet solved. In most models, MHC and CD1 proteins serve as display platforms for smaller antigens. Here, we showed that CD1a tetramers without added antigen stained large T cell pools in every subject tested, accounting for approximately 1% of skin T cells. The mechanism of tetramer binding to T cells did not require any defined antigen. Binding occurred with approximately 100 lipid ligands carried by CD1a proteins, but could be tuned upward or downward with certain natural self-lipids. TCR recognition mapped to the outer A' roof of CD1a at sites remote from the antigen exit portal, explaining how TCRs can bind CD1a rather than carried lipids. Thus, a major antigenic target of CD1a T cell autoreactivity in vivo is CD1a itself. Based on their high frequency and prevalence among donors, we conclude that CD1a-specific, lipid-independent T cells are a normal component of the human skin T cell repertoire. Bypassing the need to select antigens and effector molecules, CD1a tetramers represent a simple method to track such CD1a-specific T cells from tissues and in any clinical disease.

MHC Restriction: Where Are We Now?

MHC Restriction: Where Are We Now?

A case of pulmonary langerhans' cell histiocytosis mimicking osteosarcoma pulmonary metastases (clinical case)

Langerhans cell histiocytosis is a clonal neoplastic process characterized by cell proliferation of the Langerhans type, with the expression of CD1a, CD207 and S100 proteins and the presence of Birbek granules. We present a case of a 31-year-old woman with a verified osteosarcoma of the proximal epimetaphysis of the left tibia. Also she has multiple thin-walled cysts and foci in the lungs. The case is interesting for the rare combination of osteosarcoma of the bone and pulmonary histiocytosis. This case show that foci in lungs can simulates metastatic disease according to computed tomography (CT). Multidisciplinary approach of pathologist, oncologist and radiologist help revealed diagnose.

Inhibition of endocytic lipid antigen presentation by common lipophilic environmental pollutants

Environmental pollutants as non-heritable factors are now recognized as triggers for multiple human inflammatory diseases involving T cells. We postulated that lipid antigen presentation mediated by cluster of differentiation 1 (CD1) proteins for T cell activation is susceptible to lipophilic environmental pollutants. To test this notion, we determined whether the common lipophilic pollutants benzo[a]pyrene and diesel exhaust particles impact on the activation of lipid-specific T cells. Our results demonstrated that the expression of CD1a and CD1d proteins, and the activation of CD1a- and CD1d-restricted T cells were sensitively inhibited by benzo[a]pyrene even at the low concentrations detectable in exposed human populations. Similarly, diesel exhaust particles showed a marginal inhibitory effect. Using transcriptomic profiling, we discovered that the gene expression for regulating endocytic and lipid metabolic pathways was perturbed by benzo[a]pyrene. Imaging flow cytometry also showed that CD1a and CD1d proteins were retained in early and late endosomal compartments, respectively, supporting an impaired endocytic lipid antigen presentation for T cell activation upon benzo[a]pyrene exposure. This work conceptually demonstrates that lipid antigen presentation for T cell activation is inhibited by lipophilic pollutants through profound interference with gene expression and endocytic function, likely further disrupting regulatory cytokine secretion and ultimately exacerbating inflammatory diseases.

Lipophilic air pollutants inhibit endocytic lipid antigen presentation

Abstract Air pollutants as non-heritable factors are recognized as triggers for various human inflammatory diseases, in which T cells are central in producing cytokines and determining disease outcomes. We postulated that lipid antigen presentation mediated by cluster of differentiation 1 (CD1) proteins for T cell activation is susceptible to lipophilic air pollutants. To test this notion, we determined whether common lipophilic pollutants benzo[a]pyrene and diesel exhaust particles impact on the activation of lipid-specific T cells. Our results demonstrated that the expression of CD1a and CD1d proteins, and the activation of CD1a- and CD1d-restricted T cells were sensitively inhibited by benzo[a]pyrene even at low concentrations detectable in exposed human populations. Similarly, diesel exhaust particles showed marginal inhibitory effect. Using transcriptomic profiling, we discovered that gene expression for regulating endocytic and lipid metabolic pathways was perturbed by benzo[a]pyrene. Imaging flow cytometry also showed that CD1a and CD1d proteins were respectively retained in early and late endosomal compartments, supporting an impaired endocytic lipid antigen presentation for T cell activation upon benzo[a]pyrene exposure. This work conceptually demonstrates that lipid antigen presentation for T cell activation is inhibited by lipophilic pollutants through profound interference with gene expression and endocytic function, likely further disrupting regulatory cytokine secretion and ultimately exacerbating inflammatory diseases.

Donor-unrestricted T cells in the human CD1 system.

The CD1 and MHC systems are specialized for lipid and peptide display, respectively. Here, we review evidence showing how cellular CD1a, CD1b, CD1c, and CD1d proteins capture and display many cellular lipids to T cell receptors (TCRs). Increasing evidence shows that CD1-reactive T cells operate outside two classical immunogenetic concepts derived from the MHC paradigm. First, because CD1 proteins are non-polymorphic in human populations, T cell responses are not restricted to the donor's genetic background. Second, the simplified population genetics of CD1 antigen-presenting molecules can lead to simplified patterns of TCR usage. As contrasted with donor-restricted patterns of MHC-TCR interaction, the donor-unrestricted nature of CD1-TCR interactions raises the prospect that lipid agonists and antagonists of T cells could be developed.

Human autoreactive T cells recognize CD1b and phospholipids

In contrast with the common detection of T cells that recognize MHC, CD1a, CD1c, or CD1d proteins, CD1b autoreactive T cells have been difficult to isolate in humans. Here we report the development of polyvalent complexes of CD1b proteins and carbohydrate backbones (dextramers) and their use in identifying CD1b autoreactive T cells from human donors. Activation is mediated by αβ T-cell receptors (TCRs) binding to CD1b-phospholipid complexes, which is sufficient to activate autoreactive responses to CD1b-expressing cells. Using mass spectrometry and T-cell responses to scan through the major classes of phospholipids, we identified phosphatidylglycerol (PG) as the immunodominant lipid antigen. T cells did not discriminate the chemical differences that distinguish mammalian PG from bacterial PG. Whereas most models of T-cell recognition emphasize TCR discrimination of differing self and foreign structures, CD1b autoreactive T cells recognize lipids with dual self and foreign origin. PG is rare in the cellular membranes that carry CD1b proteins. However, bacteria and mitochondria are rich in PG, so these data point to a more general mechanism of immune detection of infection- or stress-associated lipids.

Lipid and small-molecule display by CD1 and MR1.

The antigen-presenting molecules CD1 and MHC class I-related protein (MR1) display lipids and small molecules to T cells. The antigen display platforms in the four CD1 proteins are laterally asymmetrical, so that the T cell receptor (TCR)-binding surfaces are comprised of roofs and portals, rather than the long grooves seen in the MHC antigen-presenting molecules. TCRs can bind CD1 proteins with left-sided or right-sided footprints, creating unexpected modes of antigen recognition. The use of tetramers of human CD1a, CD1b, CD1c or MR1 proteins now allows detailed analysis of the human T cell repertoire, which has revealed new invariant TCRs that bind CD1b molecules and are different from those that define natural killer T cells and mucosal-associated invariant T cells.

The role of 18FDG, 18FDOPA PET/CT and 99mTc bone scintigraphy imaging in Erdheim–Chester disease

Erdheim–Chester disease (ECD) is a rare non-Langerhans cell histiocitosis, characterized by multisystemic xanthogranulomatous infiltration by foamy histiocytes that stain positively for CD68 marker but not express CD1a and S100 proteins. Etiology and pathogenesis are still unknown and only about 500 cases are related in the literature. Multisystemic involvement leads to a wide variety of clinical manifestations that results in a poor prognosis although recent advances in treatment. We present the clinical, nuclear medicine findings and therapeutic aspects of a serie of 6 patients with histopathological diagnosis of ECD, who have undergone both bone scintigraphy (BS) and 18F-fluorodeoxyglucose (18FDG)-PET/CT scans in our institution. A complementary 18F-fluorodopa (18FDOPA)-PET/CT was performed in one case. Three different presentations of the disease were observed in our casuistic: most indolent form was a cutaneous confined disease, presented in only one patient. Multifocal involvement with central nervous system (CNS) preservation was observed in two patients. Most aggressive form consisted in a systemic involvement with CNS infiltration, presented in three patients. In our experience neurological involvement, among one case with isolate pituitary infiltration, was associated with mortality in all cases. 18FDG-PET/CT and BS were particularly useful in despite systemic involvement; locate the site for biopsy and the treatment response evaluation. By our knowledge, 18FDOPA-PET/CT not seems useful in the initial staging of ECD. A baseline 18FDG-PET/CT and BS may help in monitoring the disease and could be considered when patients were incidentally diagnosed and periodically 18FDG-PET/CT must be performed in the follow up to evaluate treatment response.

Bee venom processes human skin lipids for presentation by CD1a.

Venoms frequently co-opt host immune responses, so study of their mode of action can provide insight into novel inflammatory pathways. Using bee and wasp venom responses as a model system, we investigated whether venoms contain CD1-presented antigens. Here, we show that venoms activate human T cells via CD1a proteins. Whereas CD1 proteins typically present lipids, chromatographic separation of venoms unexpectedly showed that stimulatory factors partition into protein-containing fractions. This finding was explained by demonstrating that bee venom-derived phospholipase A2 (PLA2) activates T cells through generation of small neoantigens, such as free fatty acids and lysophospholipids, from common phosphodiacylglycerides. Patient studies showed that injected PLA2 generates lysophospholipids within human skin in vivo, and polyclonal T cell responses are dependent on CD1a protein and PLA2. These findings support a previously unknown skin immune response based on T cell recognition of CD1a proteins and lipid neoantigen generated in vivo by phospholipases. The findings have implications for skin barrier sensing by T cells and mechanisms underlying phospholipase-dependent inflammatory skin disease.

SP0053 Human T Cells Recognize CD1A Antigen Presenting Molecules Bound to Lipid Autoantigens

For decades, human alpha beta T cells were thought to solely or predominantly recognize peptide antigens bound to MHC proteins. However CD1 proteins bind diverse lipid antigens and display them...

Human CD1a Deficiency Is Common and Genetically Regulated

CD1 proteins evolved to present diverse lipid Ags to T cells. In comparison with MHC proteins, CD1 proteins exhibit minimal allelic diversity as a result of nonsynonymous single nucleotide polymorphisms (SNPs). However, it is unknown if common SNPs in gene regulatory regions affect CD1 expression and function. We report surprising diversity in patterns of inducible CD1a expression on human dendritic cells (DCs), spanning the full range from undetectable to high density, a finding not seen with other CD1 isoforms. CD1a-deficient DCs failed to present mycobacterial lipopeptide to T cells but had no defects in endocytosis, cytokine secretion, or expression of costimulatory molecules after LPS treatment. We identified an SNP in the 5' untranslated region (rs366316) that was common and strongly associated with low CD1a surface expression and mRNA levels (p = 0.03 and p = 0.001, respectively). Using a CD1a promoter-luciferase system in combination with mutagenesis studies, we found that the polymorphic allele reduced luciferase expression by 44% compared with the wild-type variant (p < 0.001). Genetic regulation of lipid Ag presentation by varying expression on human DCs provides a mechanism for achieving population level differences in immune responses despite limited structural variation in CD1a proteins.

Comparative lipidomics reveals a global sampling of major cellular membrane lipids by human CD1 proteins (P5006)

Abstract Human CD1 proteins have differentially shaped grooves and present bacterial or self lipid antigens to T cells, but it is unknown whether the pool of endogenous lipids are differently sampled by each type of CD1 proteins. We used recently established lipidomic approach to analyze the molecules extracted from human CD1a, CD1b, CD1c, and CD1d proteins. In the study, we demonstrated that this highly sensitive and accurate lipidomic approach detected more than one thousand diverse molecules defined by accurate mass retention time values, which represented hundreds of lipid species associated with CD1 proteins. More than fifty percent of these molecules were shared by all four types of CD1 proteins and additional thirty percent shared by two or three CD1 isoforms. Further mass spectrometry analyses of collision-induced dissociation showed that the molecules eluted from all four types of CD1 proteins mainly are lipids from subcellular membranes, including phospholipids of conventional, ether-linked, and lyso forms and sphingolipids. Surprisingly, CD1 isoforms with bigger grooves preferred to lipids with shorter chains, which can be explained by small spacer or scaffold lipids that bind together with antigens. Whereas previous studies argued that one lipid molecule blocks CD1 grooves, analogous to MHC class II-associated CLIP peptide, we conclude that CD1 proteins broadly sample cellular lipids and two small lipids are able to be adapted into a big groove.

Immunogenetic regulation of HLA-DR, DQ, DP and CD1a positive cells in the pathogenesis of keloid and hypertrophic scar

Recent studies have shown that HLA-DR, DQ, DP and CD1a positive cells were related to keloid and hypertrophic scar. Therefore, this study was aimed at investigating the role of immunogenetic factors in the pathogenesis of keloid and hypertrophic scar. The expression levels and distribution patterns of HLA-DR, -DQ, -DP and CD1a molecules in peripheral blood mononuclear cells were determined in 10 samples of keloid, hypertrophic scar, flat scar and normal people with the stain of streptavidin-peroxidase (SP) method. The results show that although the amounts of HLA-DR+, -DQ+, -DP+ and CD1a+ cells had no significant differences among the keloid, hypertrophic scar, flat scar and normal people groups (P>0.05), the integrated optical density (IOD) of HLA- DR+, -DQ+, -DP+ and CD1a+ cells in the keloid and hypertrophic scar were higher respectively, than that in the flat scar and normal people groups (P<0.05). The increased content of HLA-DR, -DQ, -DP and CD1a proteins in peripheral blood of the keloid and hypertrophic scar groups therefore suggest that the over-hyperplasia of scars may be associated with immunogenetic factors. Key words: Keloids, hypertrophic scars, human leukocyte antigen (HLA), CD1a.

A case of Langerhans cell histiocytosis following acute basophilic leukemia

Dear Editor, Langerhans cell histiocytosis (LCH) is a class of histiocytic cell neoplasm with a clonal neoplastic proliferation of Langerhans-type cells that express CD1a, langerin, and S100 protein and show evidence of Birbeck granules by ultrastructural examination [1]. Concurrent LCH and malignancy have been reported occasionally. LCH occurred before or after malignancies including acute lymphoblastic leukemia, acute myeloid leukemia, and several solid tumors such as malignant lymphoma, retinoblastoma, lung carcinoma, ependymoma, hepatocellular carcinoma, Askin tumor, etc. [2–5]. We present the case of a 38-year-old patient who was diagnosed with LCH following acute basophilic leukemia (ABL). A 38-year-old male presented to the emergency department with a 2-month history of indigestion, nausea, and easy fatigue. Complete blood count with differential showed a white blood cell count of 13,500/μL with 13 % blasts and 14 % basophils, 8.4 g/dL hemoglobin, and a platelet count of 110,000/μL. Hepatosplenomegaly and multiple lymphadenopathies were noted. Bone marrow (BM) aspirates showed 15.6 % leukemic blasts and 11.6 % basophils. Since marked dilution of BM aspirate specimens, the proportion of blasts and basophiles were inaccurate. However, the BM cellularity was approximately 100 % with leukemic blasts. The blasts were of medium-to-large size, had round or cleaved nuclei, contained one or two nucleoli, and a had small amount of bluish cytoplasm. Some blasts had basophilic granules (Fig. 1). Flow cytometric analysis confirmed the presence of the surface markers CD34, CD13, CD33, CD117, and CD65. The blasts showed negative reaction for myeloperoxidase, periodic acid stain, and nonspecific esterase but metachromatic positivity after staining with toluidine blue. Electron microscopy confirmed the presence of basophilic granules in blasts (Fig. 1). The karyotype analysis demonstrated trisomy 16 (47,XY,+16[3]/46,XY[17]). The patient was diagnosed with ABL and received induction chemotherapy. Three months after induction chemotherapy, multiple erythematous indurated patches were observed on the left lower abdomen. Skin biopsy showed evidence of diffuse neutrophilic infiltration with papillary dermal edema and eczematous lesions, without evidence of cancer or fungal infection. Follow-up of BM studies revealed a normocellular marrow with 4.0 % blasts. However, marked increase of histiocytic cells, including immature forms, was noted. The histiocytic cells were clustered in a nodular pattern on the BM clot section. They were of medium-to-large size, with grooved or lobulated nuclei, inconspicuous nucleoli, and moderate amount of homogeneous pinkish cytoplasm. The histiocytic cells were positive for CD1a, S100, and CD68 marker proteins by immunohistochemistry staining (Fig. 2). Based on the morphology and immunohistochemical staining profiles, the patient was diagnosed with BM involvement of LCH. However, a primary lesion of LCH was not found. The patient underwent haploidentical BM transplantation; however, his clinical course continued to deteriorate with systemic fungal infection, necrotizing pneumonia, and hemodynamic instability. Despite aggressive treatment, the patient expired 7 months after diagnosis of ABL. T.-D. Jeong : S. Jang (*) :C.-J. Park :H.-S. Chi Department of Laboratory Medicine, College of Medicine, University of Ulsan and Asan Medical Center, 88, Olympic-ro 43-gil, Songpa-gu, Seoul 138-736, South Korea e-mail: ssjang@amc.seoul.kr

A CD1 lipidomic analysis determines the structures of human CD1b scaffold lipids and its function to enhance mycobacterial antigen presentation (106.43)

Abstract Unlike the dominant role of one class II invariant chain peptide (CLIP) in blocking MHC class II, comparative lipidomics analysis shows that human CD1a, CD1b, CD1c and CD1d proteins bind lipids corresponding to hundreds of diverse accurate mass retention time values. Although most ions were observed in association with several CD1 proteins, ligands binding selectively to one CD1 isoform allowed the study of how differing antigen binding grooves influence lipid capture. The CD1b groove is distinguished by its unusually large volume, however, the average mass of compounds eluted from CD1b was similar to that of lipids from other CD1 proteins. Elution of small ligands from the large CD1b groove might be explained, if two small lipids bind simultaneously in the groove. In the context of the known CD1b crystal structures with scaffold lipids seated below the antigen, we also found that ligands selectively associated with CD1b lacked the hydrophilic head group, which is generally needed for antigen recognition, but interferes with scaffold function. Furthermore, we identified the scaffolds as deoxyceramides and diacylglycerols and directly demonstrated a function in augmenting presentation of a mycobacterial antigen, the short chain glucose monomycolate, to T cells. Thus, unlike MHC class II, CD1 proteins capture highly diverse ligands in the secretory pathway. CD1b has a mechanism for binding two small lipids to enhance bacterial antigen presentation and T cell activation.