Ectopic T cell receptor expression causes B cell immunodeficiency in transgenic mice

Mice expressing transgenic T cell receptors (TCR) are used to explore important questions in immunity. However, transgene expression may have unexpected effects. We previously reported a B cell immunodeficiency, comprising decreased B cell numbers and diminished antibody responses, in mice that express a transgenic TCR specific for nicotinic acetylcholine receptor; the mice were generated using cassette vectors designed specifically for transgenic TCR expression [see Kouskoff et al. J. Immunol. Methods 1995. 180: 273-280]. We now show data suggesting that this defect is due to the expression and accumulation of TCR alpha and beta chains inside B cells and induction of an endoplasmic reticulum stress response, causing apoptosis at the pre B-I and later B cell stage. Thus, inappropriate transgene expression can profoundly affect B cells, leading to a previously undescribed mechanism of immunodeficiency.     

Clonal composition and persistence of antigen-specific circulating T follicular helper cells

T follicular helper (T_FH) cells play an essential role in promoting B cell responses and antibody affinity maturation in germinal centers (GC). A subset of memory CD4⁺ T cells expressing the chemokine receptor CXCR5 has been described in human blood as phenotypically and clonally related to GC T_FH cells. However, the antigen specificity and relationship of these circulating T_FH (cT_FH) cells with other memory CD4⁺ T cells remain poorly defined. Combining antigenic stimulation and T cell receptor (TCR) Vβ sequencing, we found T cells specific to tetanus toxoid (TT), influenza vaccine (Flu), or Candida albicans (C.alb) in both cT_FH and non-cT_FH subsets, although with different frequencies and effector functions. Interestingly, cT_FH and non-cT_FH cells specific for C.alb or TT had a largely overlapping TCR Vβ repertoire while the repertoire of Flu-specific cT_FH and non-cT_FH cells was distinct. Furthermore, Flu-specific but not C.alb-specific PD-1⁺ cT_FH cells had a “GC T_FH-like” phenotype, with overexpression of IL21, CXCL13, and BCL6. Longitudinal analysis of serial blood donations showed that Flu-specific cT_FH and non-cT_FH cells persisted as stable repertoires for years. Collectively, our study provides insights on the relationship of cT_FH with non-cT_FH cells and on the heterogeneity and persistence of antigen-specific human cT_FH cells.     

蛋白糖基化与细胞毒性T淋巴细胞应答

糖基化是已知的蛋白最重要的翻译后修饰。已知的蛋白糖基化有多种类型 ,其中最常见的是发生在天冬酰胺 (Ａｓ ｐａｒａｇｉｎｅ ,Ａｓｎ)的Ｎ 糖基化 (Ｎ ｌｉｎｋｅｄｇｌｙｃｏｓｙｌａｔｉｏｎ)和发生在丝氨酸 (Ｓｅｒｉｎｅ ,Ｓｅｒ)和苏氨酸 (Ｔｈｒｅｏｎｉｎｅ ,Ｔｈｒ)的Ｏ 糖基化 (Ｏ ｌｉｎｋｅｄｇｌｙｃｏｓｙｌａｔｉｏｎ)。糖蛋白中糖基的结构大小不一 ,少者仅一个单糖 ,稍复杂的寡糖链可由 12～ 15个单糖残基衍生物组成 ,甚至可多达 2 0～ 30个单糖残基。糖链的结构类型与其在肽链上共价连接的氨基酸种类有关。蛋白 (肽 )糖…     

An immunohistochemical study of immunological phenomena in minor salivary glands in patients with Sjögren's syndrome

Using different monoclonal antibodies, we performed an immunofluorescent technique on labial salivary glands in order to investigate the immunological phenomena involved in Sjögren's syndrome (SS). An aberrant expression of HLA-DR molecules was detected on cytoplasm of epithelial labial salivary cells in 9 out of 19 (47%) patients, with SS. No such expression was found in 8 patients without SS or in 3 normal controls. HLA-DQ molecules were demonstrated also in two out of ten SS patients without HLA-DR. A lymphocytic infiltration was not correlated with the expression of class II molecules. T cells bearing receptors were not detected. The intracellular adhesion molecules (ICAM-1) and lymphocyte function associated antigen-1 (LFA-1) were not found on epithelial glandular salivary cells of patients and controls. In conclusion, these data suggested that the absence of ICAM-1 and LFA-1 in salivary cells and the absence of infiltrating T cells bearing receptors exclude their immunopathogenetic role in SS; moreover, these data demonstrated that the aberrant expression of HLA class II molecules on epithelial salivary cells of patients with SS is not a phenomenon correlated with the lymphocytic infiltration.     

The extracellular versus intracellular mechanisms of inhibition of TCR-triggered activation in thymocytes by adenosine under conditions of inhibited adenosine deaminase

The absence or low levels of adenosine deaminase (ADA) in humans result in severe combined immunodeficiency (SCID), which is characterized by hypoplastic thymus, T lymphocyte depletion and autoimmunity. Deficiency of ADA causes increased levels of both intracellular and extracellular adenosine, although only the intracellular lymphotoxicity of accumulated adenosine is considered in the pathogenesis of ADA SCID. It is shown that extracellular but not intracellular adenosine selectively inhibits TCR-triggered up-regulation of activation markers and apoptotic events in thymocytes under conditions of ADA deficiency. The effects of intracellular adenosine are dissociated from effects of extracellular adenosine in experiments using an adenosine transporter blocker. We found that prevention of toxicity of intracellular adenosine led to survival of TCR-cross-linked thymocytes in long-term (4 days) assays, but it was not sufficient for normal T cell differentiation under conditions of inhibited ADA. Surviving TCR-cross-linked thymocytes had a non-activated phenotype due to extracellular adenosine-mediated, TCR-antagonizing signaling. Taken together the data suggest that both intracellular toxicity and signaling by extracellular adenosine may contribute to pathogenesis of ADA SCID. Accordingly, extracellular adenosine may act on thymocytes, which survived intracellular toxicity of adenosine during ADA deficiency by counteracting TCR signaling. This, in turn, could lead to failure of positive and negative selection of thymocytes, and to additional elimination of thymocytes or autoimmunity of surviving T cells.     

γ1neo-hgp100基因的体外转染表达及体内免疫保护效应

肿瘤转移是一个复杂的、多步骤的、肿瘤细胞和宿主细胞相互作用的过程，是恶性肿瘤的重要生物学行为，往往是导致病人死亡的直接原因。随着分子生物学的发展，对肿瘤转移抑制的研究已进入分子水平，nm23基因即是近年来发现并被证实与多种肿瘤的转移有关的较新的肿瘤抑制基因，该基因可能通过影响细胞内微管的聚合／解聚和G蛋白介导的信号传导，而参与肿瘤的发生和发展。     

异基因造血干细胞移植后合并慢性移植物抗宿主病患者T细胞免疫状态的研究

目的 研究异基因造血干细胞移植后合并慢性移植物抗宿主病（cGVHD）时的T细胞免疫状态。方法 应用RT-PCR扩增14例白血病异基因造血干细胞移植后合并cGVHD患者及5名正常供者的外周血T细胞受体（TCR）BV24个家族的基因序列，并通过基因扫描的方法判断TCRBV家族的克隆表达情况、CDR3克隆性质，并计算BV家族的利用率。结果 在移植后6～19个月，所有患者TCRBV家族的利用仍处于不均一状态，检测到部分BV家族缺失，部分家族出现寡克隆、单克隆T细胞增殖。在24个BV家族的表达为6／24～15／24，并且均出现1～5个单克隆家族表达。单克隆及双克隆表达分布在不同的BV家族，未发现共用的BV家族。结论 异基因造血干细胞移植后合并cGVHD患者的T细胞免疫存在缺陷。在不同的TCRBV家族出现与cGVHD相关的克隆增殖的T细胞克隆。     

T‐cell receptor profiling in cancer

Immunosequencing is a platform technology that allows the enumeration, specification and quantification of each and every B‐ and/or T‐cell in any biologic sample of interest. Thus, it provides an assessment of the level and distribution of all the clonal lymphocytes in any sample, and allows “tracking” of a single clone or multiple clones of interest over time or from tissue to tissue within a given patient. It is based on bias‐controlled multiplex PCR and high‐throughput sequencing, and it is highly accurate, standardized, and sensitive. In this review, we provide evidence that immunosequencing is becoming an important analytic tool for the emerging field of immune‐oncology, and describe several applications of this approach, including the assessment of residual disease post therapy in lymphoid malignancies, the prediction of response to immunotherapeutics of solid tumors containing tumor infiltrating lymphocytes, the identification of clonal responses in vaccination, infectious disease, bone marrow reconstitution, and autoimmunity, and the exploration of whether there are population‐based stereotyped responses to certain exposures or interventions.     

Optimizing T-cell receptor avidity with somatic hypermutation

Adoptive transfer of T cells that have been genetically modified to express an antitumor T-cell receptor (TCR) is a potent immunotherapy, but only if TCR avidity is sufficiently high. Endogenous TCRs specific to shared (self) tumor-associated antigens (TAAs) have low affinity due to central tolerance. Therefore, for effective therapy, anti-TAA TCRs with higher and optimal avidity must be generated. Here, we describe a new in vitro system for directed evolution of TCR avidity using somatic hypermutation (SHM), a mechanism used in nature by B cells for antibody optimization. We identified 44 point mutations to the Pmel-1 TCR, specific for the H-2D^b-gp100_25-33 melanoma antigen. Primary T cells transduced with TCRs containing two or three of these mutations had enhanced activity in vitro. Furthermore, the triple-mutant TCR improved in vivo therapy of tumor-bearing mice, which exhibited improved survival, smaller tumors and delayed or no relapse. TCR avidity maturation by SHM may be an effective strategy to improve cancer immunotherapy.