T细胞抗原受体的结构与功能研究进展

T细胞抗原受体(T ceIl receptor,TCR)是T细胞表面关键的受体分子。TCR特异性地识别各种多肽抗原并通过胞内区ITAM磷酸化传递抗原刺激信号,进而引发T细胞的免疫效应。TCR的活性异常将会导致自身免疫病和免疫缺陷病的发生。对于TCR结构和功能的深入研究有助于我们更好地理解免疫反应的分子机理,从而为相关免疫疾病的预防和治疗提供重要的理论依据。该文对TCR的分类、基因重排机制、受体组装方式及其结构基础、TCR对抗原的识别以及活化机制等方面的研究成果进行了总结,综述了近几年来的最新研究进展。     

Autologous immune complex nephritis associated with sickle cell trait: diagnosis of the haemoglobinopathy after renal structural and immunological studies.

A renal tubular epithelial antigen (RTE)--anti-RTE autologous immune complex nephritis associated with sickle cell anaemia (SS) has been reported, but immune complex nephritis has never been described in patients with sickle cell trait (SA). During investigation of a child with "asymptomatic proteinuria" cryoprecipitable complexes of RTE-anti-RTE were detected in the serum and granular deposits of RTE, immunoglobulins, and complement localised on the glomerular basement membranes. Morphological and ultrastructural studies showed increased mesangial matrix, sickled red blood cells in the glomeruli and vessels, and tubular and interstitial abnormalities. These findings prompted haemoglobin electrophoretic studies, which showed previously undiagnosed haemoglobin SA in this patient and her family. These observations suggest that nephritis mediated by similar immunopathogenic mechanisms may be associated with SS and SA haemoglobinopathy. Under some conditions patients with sickle cell trait may experience haemodynamic and oxygenation abnormalities, which may be aetiological factors in the immune complex nephritis associated with SS disease.     

Latex bread technique for detection of the plaque-forming cell response to teratocarcinoma tumor antigens

Summary A latex bead technique modified for measuring the plaque-forming cell (PFC) response to teratocarcinoma tumor antigens in syngeneic animals is described.With this method one can detect both the primary (IgM) and the secondary (IgG) immune response to tumor antigens. Optimal detection of the PFC response depends on the proper ratio of sheep red blood cells to latex beads and the dose of tumor cell antigen used for immunization. The presence of fetal calf serum interfered with immunization of animals and the coating of the latex beads with the tumor cell antigens. The plaques obtained in response to immunization with teratocarcinoma cell antigens varied in size, probably reflecting the complex immune response to more than one class of antigens on tumor cells.     

Latex bread technique for detection of the plaque-forming cell response to teratocarcinoma tumor antigens

A latex bead technique modified for measuring the plaque-forming cell (PFC) response to teratocarcinoma tumor antigens in syngeneic animals is described. With this method one can detect both the primary (IgM) and the secondary (IgG) immune response to tumor antigens. Optimal detection of the PFC response depends on the proper ratio of sheep red blood cells to latex beads and the dose of tumor cell antigen used for immunization. The presence of fetal calf serum interfered with immunization of animals and the coating of the latex beads with the tumor cell antigens. The plaques obtained in response to immunization with teratocarcinoma cell antigens varied in size, probably reflecting the complex immune response to more than one class of antigens on tumor cells.     

CD19-CD21 complex regulates an intrinsic Src family kinase amplification loop that links innate immunity with B-lymphocyte intracellular calcium responses

CD19 is a B-lymphocyte cell surface molecule that functions as a general response regulator or rheostat, which defines intrinsic and B-cell antigen receptor-induced signalling thresholds that are critical for humoral immunity and expansion of the peripheral B-cell pool. In addition, B-cell responses are influenced by signals transduced through a CD19-CD21 cell surface receptor complex, where the binding of complement C3d to CD21 links humoral immune responses with the innate immune system. This review outlines recent biochemical and genetic studies that characterize the signal transduction pathways utilized by this receptor complex to regulate B-cell intracellular calcium responses.     

Class II molecules on rat alveolar type II epithelial cells

Class II (Ia) molecules of the major histocompatibility complex are important in the presentation of antigen to T cells and in the regulation of the immune response. Recent studies have suggested that many epithelial cell types can express class II molecules. We examined rat alveolar type II epithelial cells, a cell which can synthesize and secrete pulmonary surface-active material, for the expression of class II antigens. Using an indirect immunofluorescent technique with a mouse anti-rat class II monoclonal antibody (OX-4), the majority of type II cells isolated from pathogen-free Sprague-Dawley rats expressed Ia antigens as determined by fluorescent microscopy and cell sorter analysis. In culture, the Ia expression was lost from type II cells. The addition of recombinant interferon-gamma to cultures of type II cells induced the expression of class II antigens. These findings suggest that class II antigen expression on type II cells may have relevance to immune responses occurring in the lung.     

Use of proteomics to define targets of T-cell immunity

The mammalian immune system has evolved to display peptides derived from microbial antigens to immune effector cells. Liberated from the intact antigens through distinct proteolytic mechanisms, these peptides are subsequently transported to the cell surface while bound to chaperone-like receptors known as major histocompatibility complex molecules. These complexes are then scrutinized by T-cells that express receptors with specificity for specific major histocompatibility complex–peptide complexes. In normal uninfected cells, this process of antigen processing and presentation occurs continuously, with the resultant array of self-antigen-derived peptides displayed on the surface of these cells. Changes in this cellular peptide array alert the immune system to changes in the intracellular environment that may be associated with infection, oncogenesis or other abnormal cellular processes, resulting in a cascade of events that result in the elimination of the abnormal cell. Since peptides play such an essential role in informing the immune system of infection with viral or microbial pathogens and the transformation of cells in malignancy, the tools of proteomics, in particular mass spectrometry, are ideally suited to study these immune responses at a molecular level. Recent advances in studies of immune responses that have utilized mass spectrometry and associated technologies are reviewed. The authors gaze into the future and look at current challenges and where proteomics will impact in immunology over the next 5 years.     

The intrinsic immunogenic properties of cancer cell lines,immunogenic cell death,and how these influence host antitumor immune responses

Modern cancer therapies often involve the combination of tumor-directed cytotoxic strategies and generation of a host antitumor immune response. The latter is unleashed by immunotherapies that activate the immune system generating a more immunostimulatory tumor microenvironment and a stronger tumor antigen-specific immune response. Studying the interaction between antitumor cytotoxic therapies, dying cancer cells, and the innate and adaptive immune system requires appropriate experimental tumor models in mice. In this review, we discuss the immunostimulatory and immunosuppressive properties of cancer cell lines commonly used in immunogenic cell death (ICD) studies being apoptosis or necroptosis. We will especially focus on the antigenic component of immunogenicity. While in several cancer cell lines the epitopes of endogenously expressed tumor antigens are known, these intrinsic epitopes are rarely determined in experimental apoptotic or necroptotic ICD settings. Instead by far the most ICD research studies investigate the antigenic response against exogenously expressed model antigens such as ovalbumin or retroviral epitopes (e.g., AH1). In this review, we will argue that the immune response against endogenous tumor antigens and the immunopeptidome profile of cancer cell lines affect the eventual biological readouts in the typical prophylactic tumor vaccination type of experiments used in ICD research, and we will propose additional methods involving immunopeptidome profiling, major histocompatibility complex molecule expression, and identification of tumor-infiltrating immune cells to document intrinsic immunogenicity following different cell death modalities.Subject terms: Cancer models, Antigen-presenting cells, Immune cell death     

The killer's kiss: the many functions of NK cell immunological synapses

Natural killer (NK) cells comprise a subset of lymphocytes involved in protection against microbial pathogens and tumors. NK cells recognize host cells that are missing MHC class I molecules and eliminate them through localized delivery of lytic granules. The majority of NK cell effector functions require direct cell-to-cell contact. Binding to a target cell is accompanied by creation of complex structures at the cell-cell interface known as immunological synapses. Recent studies have contributed immensely to the characterization of several types of NK cell immunological synapses and understanding of the variety of processes originating at this intriguing place. The emerging picture illustrates NK cell immune synapses as the sites of highly complex regulation of NK cell activity.     

IgE immune complexes stimulate an increase in lung mast cell progenitors in a mouse model of allergic airway inflammation

Mast cell numbers and allergen specific IgE are increased in the lungs of patients with allergic asthma and this can be reproduced in mouse models. The increased number of mast cells is likely due to recruitment of mast cell progenitors that mature in situ. We hypothesized that formation of IgE immune complexes in the lungs of sensitized mice increase the migration of mast cell progenitors to this organ. To study this, a model of allergic airway inflammation where mice were immunized with ovalbumin (OVA) in alum twice followed by three daily intranasal challenges of either OVA coupled to trinitrophenyl (TNP) alone or as immune complexes with IgE-anti-TNP, was used. Mast cell progenitors were quantified by a limiting dilution assay. IgE immune complex challenge of sensitized mice elicited three times more mast cell progenitors per lung than challenge with the same dose of antigen alone. This dose of antigen challenge alone did not increase the levels of mast cell progenitors compared to unchallenged mice. IgE immune complex challenge of sensitized mice also enhanced the frequency of mast cell progenitors per 10(6) mononuclear cells by 2.1-fold. The enhancement of lung mast cell progenitors by IgE immune complex challenge was lost in FcRγ deficient mice but not in CD23 deficient mice. Our data show that IgE immune complex challenge enhances the number of mast cell progenitors in the lung through activation of an Fc receptor associated with the FcRγ chain. This most likely takes place via activation of FcεRI, although activation via FcγRIV or a combination of the two receptors cannot be excluded. IgE immune complex-mediated enhancement of lung MCp numbers is a new reason to target IgE in therapies against allergic asthma.     

Isolation,Processing and Analysis of Murine Gingival Cells

We have developed a technique to precisely isolate and process murine gingival tissue for flow cytometry and molecular studies. The gingiva is a unique and important tissue to study immune mechanisms because it is involved in host immune response against oral biofilm that might cause periodontal diseases. Furthermore, the close proximity of the gingiva to alveolar bone tissue enables also studying bone remodeling under inflammatory conditions. Our method yields large amount of immune cells that allows analysis of even rare cell populations such as Langerhans cells and T regulatory cells as we demonstrated previously ¹. Employing mice to study local immune responses involved in alveolar bone loss during periodontal diseases is advantageous because of the availability of various immunological and experimental tools. Nevertheless, due to their small size and the relatively inconvenient access to the murine gingiva, many studies avoided examination of this critical tissue. The method described in this work could facilitate gingival analysis, which hopefully will increase our understating on the oral immune system and its role during periodontal diseases.     

From Tumor Necrosis Factor Receptor to RANK, from the Selectins and Link Proteins to CD44: New Molecular Models of Cell Surface Receptors and Analysis of Specificity Determinants

Modeling and structure-function studies on two cell surface proteins are presented, which are implicated in the regulation of immune responses and cell adhesion. In the first part, model building of RANK, a new member of the tumor necrosis factor receptor (TNFR) superfamily (TNFRSF), is reported. The model is analyzed in light of structural studies on the TNFR-ligand complex and molecular model-based mutagenesis analyses of CD40-ligand and Fas-ligand interactions. The study makes it possible to predict residues important for ligand binding to RANK and further rationalizes differences in specificity between TNFR-like cell surface receptors. In the second part, recent investigations on the structure and carbohydrate binding site of CD44, a member of the link protein family, are discussed. The binding site in CD44 is compared to calcium-dependent (C-type) lectins, which include the selectins, another family of cell adhesion molecules. The studies on TNFRSF members and link proteins reported herein complement a recent review article in this journal, which focused on modeling and binding site analysis of immune cell surface proteins.Electronic Supplementary Material available.     

Tumor-induced perturbations of cytokines and immune cell networks

Until recently, the intrinsically high level of cross-talk between immune cells, the complexity of immune cell development, and the pleiotropic nature of cytokine signaling have hampered progress in understanding the mechanisms of immunosuppression by which tumor cells circumvent native and adaptive immune responses. One technology that has helped to shed light on this complex signaling network is the cytokine antibody array, which facilitates simultaneous screening of dozens to hundreds of secreted signal proteins in complex biological samples. The combined applications of traditional methods of molecular and cell biology with the high-content, high-throughput screening capabilities of cytokine antibody arrays and other multiplexed immunoassays have revealed a complex mechanism that involves multiple cytokine signals contributed not just by tumor cells but by stromal cells and a wide spectrum of immune cell types. This review will summarize the interactions among cancerous and immune cell types, as well as the key cytokine signals that are required for tumors to survive immunoediting in a dormant state or to grow and spread by escaping it. Additionally, it will present examples of how probing secreted cell–cell signal networks in the tumor microenvironment (TME) with cytokine screens have contributed to our current understanding of these processes and discuss the implications of this understanding to antitumor therapies.     

Emerging role of RNA modification N6-methyladenosine in immune evasion

The innate and adaptive immune cells have complex signaling pathways for sensing and initiating immune responses against disease. These pathways are interrupted at different levels to occur immune evasion, including by N6-methyladenosine (m6A) modification. In this review, we discuss studies revealing the immune evasion mechanism by m6A modification, which underlies the retouching of these signaling networks and the rapid tolerance of innate and adaptive immune molecules during disease. We also focus on the functions of m6A in main chemokines regulation, and their roles in promotive and suppressive immune cell recruitment. We then discuss some of the current challenges in the field and describe future directions for the immunological mechanisms of m6A modification.Subject terms: Immunosurveillance, RNA modification     

Exploiting Gene-Expression Deconvolution to Probe the Genetics of the Immune System

Sequence variation can affect the physiological state of the immune system. Major experimental efforts targeted at understanding the genetic control of the abundance of immune cell subpopulations. However, these studies are typically focused on a limited number of immune cell types, mainly due to the use of relatively low throughput cell-sorting technologies. Here we present an algorithm that can reveal the genetic basis of inter-individual variation in the abundance of immune cell types using only gene expression and genotyping measurements as input. Our algorithm predicts the abundance of immune cell subpopulations based on the RNA levels of informative marker genes within a complex tissue, and then provides the genetic control on these predicted immune traits as output. A key feature of the approach is the integration of predictions from various sets of marker genes and refinement of these sets to avoid spurious signals. Our evaluation of both synthetic and real biological data shows the significant benefits of the new approach. Our method, VoCAL, is implemented in the freely available R package ComICS.     

Use of proteomics to define targets of T-cell immunity

The mammalian immune system has evolved to display peptides derived from microbial antigens to immune effector cells. Liberated from the intact antigens through distinct proteolytic mechanisms, these peptides are subsequently transported to the cell surface while bound to chaperone-like receptors known as major histocompatibility complex molecules. These complexes are then scrutinized by T-cells that express receptors with specificity for specific major histocompatibility complex-peptide complexes. In normal uninfected cells, this process of antigen processing and presentation occurs continuously, with the resultant array of self-antigen-derived peptides displayed on the surface of these cells. Changes in this cellular peptide array alert the immune system to changes in the intracellular environment that may be associated with infection, oncogenesis or other abnormal cellular processes, resulting in a cascade of events that result in the elimination of the abnormal cell. Since peptides play such an essential role in informing the immune system of infection with viral or microbial pathogens and the transformation of cells in malignancy, the tools of proteomics, in particular mass spectrometry, are ideally suited to study these immune responses at a molecular level. Recent advances in studies of immune responses that have utilized mass spectrometry and associated technologies are reviewed. The authors gaze into the future and look at current challenges and where proteomics will impact in immunology over the next 5 years.     

Induction of protective immunity to Friend murine leukemia virus in genetic nonresponders to virus envelope protein

(B10.A x A/WySn)F1, H-2a/a, mice are genetic nonresponders to the envelope protein of Friend murine leukemia helper virus (F-MuLV) when immunized with a recombinant vaccinia virus expressing F-MuLV env gene. In contrast these mice can be protectively immunized against leukemogenic Friend virus complex using formalin-fixed F-MuLV virions in CFA. To determine which viral proteins were responsible for this immune protection, virion proteins prepared by SDS-PAGE and electroelution were used to immunize mice. Purified gp70 envelope protein in CFA was capable of inducing strong immune protection against the challenge with Friend virus complex in H-2a/a mice. Immunologic studies demonstrated that immunized mice developed a virus-specific T cell proliferative response and showed IgM to IgG Ig class switching of virus-neutralizing antibodies. These results indicated that genetically controlled immune nonresponsiveness to F-MuLV envelope Ag in H-2a/a mice could be overcome using denatured viral envelope protein together with a strong adjuvant.     

A meta-analysis of the existing knowledge of immunoreactivity against hepatitis C virus (HCV)

Approximately 3% of the world population is infected by HCV, which represents a major global health challenge. Almost 400 different scientific reports present immunological data related to T cell and antibody epitopes derived from HCV literature. Analysis of all HCV-related epitope hosted in the Immune Epitope Database (IEDB), a repository of freely accessible immune epitope data, revealed more than 1500 and 1900 distinct T cell and antibody epitopes, respectively. The inventory of all data revealed specific trends in terms of the host and the HCV genotypes from which sequences were derived. Upon further analysis we found that this large number of epitopes reflects overlapping structures, and homologous sequences derived from different HCV isolates. To access and visualize this information we developed a novel strategy that assembles large sets of epitope data, maps them onto reference genomes and displays the frequency of positive responses. Compilation of the HCV immune reactivity from hundreds of different studies, revealed a complex and thorough picture of HCV immune epitope data to date. The results pinpoint areas of more intense reactivity or research activities at the level of antibody, CD4 and CD8 responses for each of the individual HCV proteins. In general, the areas targeted by the different effector immune functions were distinct and antibody reactivity was positively correlated with hydrophilicity, while T cell reactivity correlated with hydrophobicity. At the sequence level, epitopes frequently recognized by both T cell and B cell correlated with low variability, and our analysis thus highlighted areas of potential interest for practical applications. The human reactivity was further analyzed to pinpoint differential patterns of reactivity associated with acute versus chronic infection, to reveal the apparent impact of glycosylation on T cell, but not antibody responses, and to highlight a paucity of studies involved antibody epitopes associated with virus neutralization.     

Quantitation of a src-like tyrosine protein kinase during fertilization of the sea urchin egg

Fertilization of the sea urchin egg is known to involve an increase in overall protein tyrosine kinase activity which precede the first cell division. In order to determine the types of tyrosine kinases that are involved in fertilization, we have used immunological and other criteria to identify a c-src related protein kinase in eggs of the sea urchin L. variegatus. Using an immune complex assay, we have measured the level of this c-src related protein kinase during fertilization and early embryonic development. Fertilization results in a decrease in the c-src kinase detectable by this technique suggesting that c-src does not contribute to the fertilization induced increase in protein tyrosine kinase activity.     

The use of radioimmune assay in investigating reagents to be used in the immunocytochemical localization of hepatitis B surface antigen in immune complexes in the kidney of patients with membranous nephropathy and Australia antigenaemia

Radioimmune assay (RIA) was used to investigate the effect of fixatives on antigenicity of the hepatitis B surface antigen (HBsAg) and the effect of pronase on the elution of antibody (Ab) from the HBsAG-Ab complex. The effect of pronase on Ab elution was also tested on sections of kidney from a patient with the immune complex disease systemic lupus erythematosus (SLE). Immunoglobulin G (IgG) was located in pronase treated and untreated sections using the indirect immunoperoxidase technique. Glutaraldehyde was shown to be the fixative of choice for studies involving HbsAG. All fixatives were shown to have less effect on antigenicity at 4 degrees C than at room temperature. Osmium tetroxide reduced antigenicity to one-third, even at 4 degrees C. RIA and SLE kidney section studies showed that Ab was eluted from immune complexes by pronase. Pre-fixation of the antigen (Ag) by glutaraldehyde appears to have no effect on the final elution, although fixation after pronase treatment seemed to enhance the elution effects. The availability of an RIA kit with HBsAg- and AB-coated beads was of great assistance in evaluating reagents to be used in immunoperoxidase studies of HBsAg in immune complexes of patients with membranous nephropathy and Australia antigenaemia.