Single-cell fate mapping reveals widespread clonal ignorance of low-affinity T cells exposed to systemic infection

T cell ignorance is a specific form of immunological tolerance. It describes the maintenance of naivety in antigen-specific T cells in vivo despite the presence of their target antigen. It is thought to mainly play a role during the steady state, when self-antigens are presented in absence of costimulatory signals and at low density or to T cells of low affinity. In how far antigen-specific T cells can also remain clonally ignorant to foreign antigens, presented in the inflammatory context of systemic infection, remains unclear. Using single-cell in vivo fate mapping and high throughput flow cytometric enrichment, we find that high-affinity antigen-specific CD8⁺ T cells are efficiently recruited upon systemic infection. In contrast, most low-affinity antigen-specific T cells ignore the priming antigen and persist in the naïve state while remaining fully responsive to subsequent immunization with a high-affinity ligand. These data establish the widespread clonal ignorance of low-affinity T cells as a major factor shaping the composition of antigen-specific CD8⁺ T cell responses to systemic infection.     

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.     

Enolase 1 of Candida albicans binds human CD4+ T cells and modulates naïve and memory responses

To obtain a better understanding of the biology behind life-threatening fungal infections caused by Candida albicans, we recently conducted an in silico screening for fungal and host protein interaction partners. We report here that the extracellular domain of human CD4 binds to the moonlighting protein enolase 1 (Eno1) of C. albicans as predicted bioinformatically. By using different anti-CD4 monoclonal antibodies, we determined that C. albicans Eno1 (CaEno1) primarily binds to the extracellular domain 3 of CD4. Functionally, we observed that CaEno1 binding to CD4 activated lymphocyte-specific protein tyrosine kinase (LCK), which was also the case for anti-CD4 monoclonal antibodies tested in parallel. CaEno1 binding to naïve human CD4⁺ T cells skewed cytokine secretion toward a Th2 profile indicative of poor fungal control. Moreover, CaEno1 inhibited human memory CD4⁺ T-cell recall responses. Therapeutically, CD4⁺ T cells transduced with a p41/Crf1-specific T-cell receptor developed for adoptive T-cell therapy were not inhibited by CaEno1 in vitro. Together, the interaction of human CD4⁺ T cells with CaEno1 modulated host CD4⁺ T-cell responses in favor of the fungus. Thus, CaEno1 mediates not only immune evasion through its interference with complement regulators but also through the direct modulation of CD4⁺ T-cell responses.     

Mechanistic insight of interleukin-9 induced osteoclastogenesis

Interleukin (IL)-9 is an emerging player in the pathogenesis of various chronic inflammatory diseases including bone disorders like rheumatoid arthritis (RA) and psoriatic arthritis. Recently, IL-9 was shown to enhance the osteoclast formation and their function in RA. However, the mechanisms by which IL-9 influences osteoclastogenesis are not known. Therefore, in this study we aimed to unravel the direct and indirect ways by which IL-9 can influence osteoclast formation. We used mouse bone marrow precursor cells for checking the effect of IL-9 on osteoclast differentiation and its function. Next, IL-9 induced signalling pathway were checked in the process of osteoclastogenesis. T cells play an important role in enhancing osteoclastogenesis in inflammatory conditions. We used splenic T cells to understand the impact of IL-9 on the functions of T effector (Teff) and regulatory T (Treg) cells. Furthermore, the effect of IL-9 mediated modulation of the T cell response on osteoclasts was checked using a coculture model of T cells with osteoclast precursors. We showed that IL-9 enhanced osteoclast formation and its function. We found that IL-9 activates STAT3, P38 MAPK, ERK1/2, NFκB and we hypothesize that it mediates the effect on osteoclastogenesis by accelerating mitochondrial biogenesis. Additionally, IL-9 was observed to facilitate the functions of pro-osteoclastogenic IL-17 producing T cells, but inhibits the function of anti-osteoclastogenic Treg cells. Our observations suggest that IL-9 can influence osteoclastogenesis directly by modulating the signalling cascade in the precursor cells; indirectly by enhancing IL-17 producing T cells and by reducing the functions of Treg cells.     

Decreased frequency of a novel T-lymphocyte subset,CD3+CD4−CD7+CD57− T cells,in hepatitis B virus-related end-stage liver disease might contribute to disease progression

CD7 and CD57 are related to the differentiation and functional stages of CD8⁺ T cells. However, the role of their combined presence in CD8⁺ T cells in patients with chronic hepatitis B virus (HBV) infection, especially those with end-stage liver disease, remains unclear. Blood samples from healthy volunteers and patients with chronic hepatitis B were analyzed via Luminex assay and ELISA to measure plasma cytokine levels. Further, recombinant IL-22 was used to stimulate peripheral blood mononuclear cells from healthy volunteers, and the frequency of CD3⁺CD4⁻CD7⁺CD57⁻ T cells and apoptosis rates were investigated via flow cytometry. Patients with end-stage liver disease, particularly those with acute to chronic liver failure, showed decreased CD3⁺CD4⁻CD7⁺CD57⁻ T cell frequency. Furthermore, the prevalence of CD3⁺CD4⁻CD7⁺CD57⁻ T cells was negatively correlated with disease severity, prognosis, and complications (ascites). We also observed that IL-22 promoted apoptosis and brought about a decrease in the number of CD3⁺CD4⁻CD7⁺CD57⁻ T cells in a dose-dependent manner. CD3⁺CD4⁻CD7⁺CD57⁻ T cells displayed a B and T lymphocyte attenuator (BTLA)^highCD25^highCD127^high immunosuppressive phenotype and showed low interferon-γ, tumor necrosis factor-α, granzyme A, and perforin expression levels. The present findings will elucidate the pathogenesis of HBV-related end-stage liver disease and aid the identification of novel drug targets.     

烧伤患者外周血T淋巴细胞亚群变化动态观察

为探讨烧伤后机体细胞免疫紊乱的机制,动态观察了30例不同烧伤面积患者不同时间的T淋巴细胞亚群变化情况.结果发现:中度烧伤组CD3,CD8伤后变化不大,CD4及CD4/CD8比值至伤后第二周起明显低于正常对照组:重度烧伤组,伤后一周CD3,CD4及CD4/CD8比值即明显降低,至伤后三周CD8明显高于对照组,特重烧伤组,伤后一周即出现CD3,CD4及CD4/CD8比值明显降低,而CD8则明显升高.结论:(1)烧伤后T淋巴细胞亚群的改变是烧伤患者免疫功能低下的原因之一;(2)中度烧伤患者CD/CD8比值下降,主要是由CD4下降所致而重度及特重度烧伤患者CD4/CD8比值下降则是由CD4下降和CD8上升共同作用所致;(3)烧伤面积越大,细胞免疫功能下降越明显,其发生机理越复杂.     

旱莲草乙酸乙酯总提物对小鼠外周血T淋巴细胞亚群影响

目的 :研究旱莲草乙酸乙酯总提物 (TAEEP)对正常及免疫抑制小鼠T淋巴细胞亚群的作用。方法 :采用正常及腹腔注射环磷酰胺 ( 60mg/kg)所致免疫功能低下小鼠模型 ,给予大、小剂量的TAEEP ,用流式细胞仪测定小鼠血T淋巴细胞CD4 +、CD8+亚群的比例。结果 :大、小剂量TAEEP均显著降低正常小鼠CD4 +亚群的比例 (P <0 .0 1) ,并可显著提高免疫低下小鼠CD4 +亚群比例 ,对于正常小鼠CD8+亚群的比例 ,TAEEP的小剂量可显著降低其比例 (P <0 .0 5) ,而大剂量则显著提高其比例。结论 :旱莲草乙酸乙酯总提物对小鼠外周血T淋巴细胞亚群具有调节作用。     

CD3AK细胞对烧伤患者免疫功能的影响

通过检测患者淋巴细胞转化功能及NK细胞活性,调查CD3AK细胞对烧伤患者免疫功能的影响.结果发现:CD3AK细胞使T细胞转化为母细胞能力增加,NK细胞活性升高,表明CD3AK细胞能改善烧伤患者免疫功能低下的状态,促进细胞免疫功能的恢复.     

肿瘤抗原MAGE-3预测CTL表位的合成与鉴定

目的 合成并鉴定已预测出的４个ＭＡＧＥ－３ ＨＬＡ－Ａ２限制性ＣＴＬ表位多肽,为后续研究奠定基础。方法 采用固相合成法合成多肽,经ＲＰ－ＨＰＬＣ纯化、纯度分析,用质谱进行定性鉴定。结果 ４个合成肽的纯度都在９５％以上,经质谱分析,各肽的分子量测定值与理论值相符,结论 所得多肽为高纯度的目标肽,为后续研究提供了可靠的保证。     

急性T淋巴细胞白血病细胞系JM分泌抑制因子在体外对T细胞凋亡及细胞周期的影响

目的　研究急性 T淋巴细胞白血病细胞系 JM分泌的抑制因子 (TL SFJM)在体外对 T细胞凋亡及细胞周期的影响 .方法　以 TL SFJM作用于有丝分裂原 PHA、蛋白激酶 C(PKC)活化剂 PMA和同种异体抗原 (alloantigen)活化的人或小鼠 T细胞 ,应用流式细胞仪检测细胞凋亡及细胞周期 .结果　 TL SFJM在体外可诱导 PHA/IL - 2活化的小鼠胸腺细胞的凋亡 .TL SFJM在体外可诱导 alloantigen活化的人外周血单个核细胞 (PBMC)的凋亡 ,且把细胞周期阻遏在 G1期 .TL SFJM对 PMA诱导的人 PBMC活化抗原 CD2 5的表达无明显影响 ,也不引起凋亡 .结论　 TL SFJM在体外可诱导 PHA、alloantigen活化的 T细胞凋亡 .