Regulatory T Cell Ablation Causes Acute T Cell Lymphopenia

Regulatory T (Treg) cells enforce T cell homeostasis and maintain peripheral T cell tolerance. Here we report a previously unappreciated phenomenon of acute T cell lymphopenia in secondary lymphoid organs and non-lymphoid tissues triggered by Treg cell depletion that precedes the expansion of self-reactive T cells. Lymphopenia affects both neonates and adults indicating a dominant role of Treg cells in maintaining peripheral T cell numbers regardless of the developmental stage. The lymphopenia was neither triggered by caspase-dependent apoptosis nor macrophage-mediated clearance of T cells, nor diminished survival of naïve or recently activated T cells due to paucity of IL-7. It is possible that transient lymphopenia associated with congenital or acute Treg cell deficiency may contribute to the development of T cell mediated autoimmune disorders.     

HTLV-1感染T细胞克隆扩增和转化在成人T细胞白血病表达分析

摘要 目的：探究人类T细胞白血病1型病毒（Human T-cell leukemia virus type，HTLV-1）感染的T细胞克隆扩增和转化在成人T细胞白血病（AdultT-cellleukemia，ATL）中的表达分析，探究HTLV-1在T淋巴细胞中发生克隆扩增和转化的机制，为ATL的临床治疗提供理论基础。方法：选择2015年2月至2018年2月于我院接受治疗的38例ATL患者为研究对象，按照其病程差异将其分为急性ATL组（20例）和慢性ALT组（18例），分别采集其血样并检测两组患者血样中HTLV-1病毒载量的差异性，对比两组患者样本中Tax蛋白和HMGB1蛋白的表达情况，并就两组患者血样中肿瘤坏死因子（tumor necrosis factor，TNF-α）、癌胚抗原（carcinoembryonic antigen，CEA）的水平进行对比。结果：（1）急性ATL组患者HTLV-1病毒载量明显高于慢性ATL组患者HTLV-1病毒载量（P<0.05）；（2）对比显示，急性ATL组患者血样中Tax蛋白和HMGB1蛋白表达量明显高于慢性ATL组患者（P<0.05）；（3）急性ATL组患者中TNF-α和CEA水平均明显高于慢性ATL组患者（P<0.05）。结论：HTLV-1感染ATL患者病程的差异会影响T淋巴细胞的克隆扩增和转化进程，分析其机制可能与HTLV-1能够调控Tax蛋白和HMGB1表达有关。     

EB病毒诱导的胸腺恶性T细胞淋巴瘤细胞体外长期培养研究

建立含有EB病毒的T细胞淋巴瘤细胞系,为探讨EB病毒的致瘤机理,研究EB病毒在T细胞淋巴瘤发生过程中的作用提供手段.在TPA协同EB病毒诱导胸腺恶性T细胞淋巴瘤动物模型的基础上,联合应用IL-2,将诱导的肿瘤组织进行体外细胞培养,成功地分离获得一株在体外长期存活的淋巴细胞TET.T细胞亚群分类实验证实TET细胞为CD4阳性的T淋巴细胞,PCR和原位杂交可检测到EB病毒的EBERs、LMP1和BARF1,并有LMP1蛋白的表达.TET细胞的获得,有望在体外建立转化细胞系,为体外研究EB病毒的致瘤机理及防治提供理想的实验材料.     

LMO2与T细胞白血病

Lmo2基因是LMO(LIM-only)家族的成员之一。作为一个原癌基因,Lmo2的染色体异位t(11;14)(p13;q11)或t(7;11)(q35;p13)与T细胞急性淋巴细胞白血病密切相关。LMO2是细胞中介导转录因子复合物形成的重要接头分子。现对LMO2的分子结构及其在正常和白血病细胞中的调控作用机制的差异作重点介绍。在此基础上还讨论了LMO2成为逆转录病毒介导的基因治疗X染色体连锁的严重联合免疫缺陷综合征过程中成为病毒插入靶位点的可能原因。     

计算机辅助T细胞表位鉴定

免疫相关抗原T细胞表位的鉴定与筛选是疫苗开发的关键之一。目前,基于对天然MHC配体或合成肽与MHC分子结合特性的分析,若干计算机算法已被用于MHCI／Ⅱ类分子限制性T细胞表位的预测。而且,基于对蛋白酶体裂解片段的分析,开发了预测蛋白酶体酶切位点的算法。为进一步证实预测的表位肽在体有效性及免疫原性,若干实验技术也被相继开发和应用。同时,若干方法也被用于检测活化T细胞针对表达特定抗原靶细胞的免疫识别和T细胞活化后所分泌的细胞因子的产生。该综述了计算机辅助设计在表位筛选中的应用。     

调节性T细胞的分化及其影响因素

调节性T细胞是近年发现的一种具有免疫抑制活性的CD4+T细胞亚群,它们可以在胸腺中被选择分化,也可以在外周淋巴组织内由转化生长因子-β等细胞因子诱导分化。本文就调节性T细胞分化过程的关键信号通路及影响因素进行综述。调控调节性T细胞的分化过程能够影响其在体内的数目,可通过对其数量的干预,为自身免疫性疾病、免疫监视、排斥反应及变态反应等相关疾病提供可能的治疗靶点。     

T细胞记忆的理论研究

基于CD8⁺ T记忆细胞的线性和逆线性分化假说分别建立了数学模型,并研究了各种T细胞亚类的动力学.发现在优化剂量抗原入侵的条件下,两个模型均能产生记忆,并可较好地模拟实验结果.通过进一步模拟发现CD8⁺ T细胞记忆与抗原的存在紧密相关,再次证实了抗原在维持T细胞记忆中的作用.另外还讨论了记忆细胞寿命的问题.认为逆线性假说具有更强的反应性和记忆性.     

Increased Cell Surface Free Thiols Identify Effector CD8+ T Cells Undergoing T Cell Receptor Stimulation

Recognition of peptide Major Histocompatibility Complexes (MHC) by the T cell receptor causes rapid production of reactive oxygen intermediates (ROI) in naïve CD8⁺ T cells. Because ROI such as H₂O₂ are membrane permeable, mechanisms must exist to prevent overoxidation of surface proteins. In this study we used fluorescently labeled conjugates of maleimide to measure the level of cell surface free thiols (CSFT) during the development, activation and differentiation of CD8⁺ T cells. We found that during development CSFT were higher on CD8 SP compared to CD4 SP or CD4CD8 DP T cells. After activation CSFT became elevated prior to division but once proliferation started levels continued to rise. During acute viral infection CSFT levels were elevated on antigen-specific effector cells compared to memory cells. Additionally, the CSFT level was always higher on antigen-specific CD8⁺ T cells in lymphoid compared to nonlymphoid organs. During chronic viral infection, CSFT levels were elevated for extended periods on antigen-specific effector CD8⁺ T cells. Finally, CSFT levels on effector CD8⁺ T cells, regardless of infection, identified cells undergoing TCR stimulation. Taken together these data suggest that CD8⁺ T cells upregulate CSFT following receptor ligation and ROI production during infection to prevent overoxidation of surface proteins.     

Probing the Effector and Suppressive Functions of Human T Cell Subsets Using Antigen-Specific Engineered T Cell Receptors

Activation of T cells through the engagement of the T cell receptors (TCRs) with specific peptide-MHC complexes on antigen presenting cells (APCs) is the major determinant for their proliferation, differentiation and display of effector functions. To assess the role of quantity and quality of peptide-MHC presentation in eliciting T cell activation and suppression functions, we genetically engineered human T cells with two TCRs that recognize HLA-A*0201-restricted peptides derived from either HIV or melanoma antigens. The engineered-TCRs are highly functional in both CD8⁺ and CD4⁺ T cells as assessed by the upregulation of activation markers, induction of cytokine secretion and cytotoxicity. We further demonstrated that engineered-TCRs can also be expressed on naïve human T cells, which are stimulated through APCs presenting specific peptides to induce T cell proliferation and acquire effector functions. Furthermore, regulatory T cells (Tregs) ectopically expressing the engineered-TCRs are activated in an antigen-specific fashion and suppress T cell proliferation. In this system, the inhibitory activity of peptide-stimulated Tregs require the presence of dendritic cells (DCs) in the culture, either as presenters or as bystander cells, pointing to a critical role for DCs in suppression by Tregs. In conclusion, the engineered-TCR system reported here advances our ability to understand the differentiation pathways of naïve T cells into antigen-specific effector cells and the role of antigen-specific signaling in Treg-mediated immune suppression.     

Control of Cell pH in the T84 Colon Cell Line

Cell pH regulation was investigated in the T84 cell line derived from epithelial colon cancer. Cell pH was measured by ratiometric fluorescence microscopy using the fluorescent probe BCECF. Basal pH was 7.17 ± 0.023 (n= 48) in HEPES Ringer. After acidification by an ammonium pulse, cell pH recovered toward normal at a rate of 0.13 ± 0.011 pH units/min in the presence of Na⁺, but in the absence of this ion or after treatment with 0.1 mm hexamethylene amiloride (HMA) no significant recovery was observed, indicating absence of Na⁺ independent H⁺ transport mechanisms in HEPES Ringer. In CO₂/HCO⁻ ₃ Ringer, basal cell pH was 7.21 ± 0.020 (n= 35). Changing to HEPES Ringer, a marked alkalinization was observed due to loss of CO₂, followed by return to the initial pH at a rate of −0.14 ± 0.012 (n= 8) pH/min; this return was retarded or abolished in the absence of Cl⁻ or after addition of 0.2 mm DIDS, suggesting extrusion of bicarbonate by Cl⁻/HCO⁻ ₃ exchange. This exchange was not Na⁺ dependent. When Na⁺ was added to cells incubated in 0 Na⁺ Ringer while blocking Na⁺/H⁺ exchange by HMA, cell alkalinization by 0.19 ± 0.04 (n= 11) pH units was observed, suggesting the presence of Na⁺/HCO⁻ ₃ cotransport carrying HCO⁻ ₃ into these cells, which was abolished by DIDS. These experiments, thus, show that Na⁺/H⁺ and Cl⁻/HCO⁻ ₃ exchange and Na⁺/HCO⁻ ₃ cotransport participate in cell pH regulation in T84 cells. Received: 3 April 2000/Revised: 22 June 2000     

CD45RB Status of CD8+ T Cell Memory Defines T Cell Receptor Affinity and Persistence

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Ustekinumab Improves Psoriasis without Altering T Cell Cytokine Production,Differentiation, and T Cell Receptor Repertoire Diversity

Ustekinumab is a fully human IgG1κ monoclonal antibody targeting interleukin (IL)-12/23 p40 subunit. The role of IL-12/23-mediated pathway in the mechanism of various inflammatory disorders especially psoriasis has been well recognized. Recently the long-term efficacy and safety of ustekinumab in patients with moderate-to-severe psoriasis has been evaluated in phase 2/3 clinical trials, and the results showed no significant risk for serious adverse effects, infections, or malignancies. Ustekinumab inhibits the function of the IL-12/23 p40 subunit, and therefore it is believed that inhibition of IL-12 p40 pathway decreases IFN-γ production. The major concern for the use of ustekinumab is the possibility of increased immunosuppression due to low IFN-γ production. However, the effects of ustekinumab on CD4⁺ T cell function have not been fully investigated so far. In this study, we explored changes in cytokine production by memory CD4⁺ T cells as well as in the differentiation of naïve T cells to helper T cell (Th) 1, Th2, or Th17 cells in psoriasis patients treated with ustekinumab. The effect of the treatment on T cell receptor repertoire diversity was also evaluated. The results showed that ustekinumab improves clinical manifestation in patients with psoriasis without affecting cytokine production in memory T cells, T cell maturation, or T cell receptor repertoire diversity. Although the number of patients is limited, the present study suggests that T cell immune response remains unaffected in psoriasis patients treated with ustekinumab.     

Cytoskeletal Control of Antigen-Dependent T Cell Activation

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