Homo sapiens Targeted Locus (Loci). Homo sapiens

ObjectivesAntinuclear antibody (ANA) positive Juvenile Idiopathic Arthritis (JIA) is characterized by synovial B cell hyperactivity, but the precise role of CD4+ T cells in promoting local B cell activation is unknown. The objective of this study is to unravel the phenotype and function of synovial CD4+ T cells that promote the aberrant B cell activation in JIA.MethodsFlow cytometric analysis was performed to compare the phenotype and cytokine pattern of synovial fluid (SF) PD-1hi CD4+ T cells with tonsil TFH cells. TCRVB next generation sequencing was applied to analyze T cell subsets for signs of clonal expansion. The functional impact of these T cell subsets on B cells was dissected in in vitro co-cultures.ResultsMultidimensional flow-cytometric analysis revealed the expansion of IL-21 and IFN-gamma co-expressing PD-1hiCXCR5-HLA-DR+ CD4+ T cells that accumulate in the joints of ANA+ JIA patients. These T cells exhibited signs of clonal expansion with restricted TCR clonotypes. Phenotypically they resembled peripheral T helper (TPH) cells with an extrafollicular chemokine receptor pattern and high T-bet and Blimp-1 but low Bcl-6 expression. SF TPH cells particularly skewed B cell differentiation towards a CD21lo/-CD11c+ phenotype by provision of IL-21 and IFN-gamma in vitro and correlated with the appearance of SF CD21lo/-CD11c+CD27-IgM- double-negative B cells (BDN) in situ.ConclusionClonally expanded CD4+ TPH cells accumulate in the joints of ANA+ JIA patients and particularly promote CD21lo/-CD11c+BDN cell differentiation The expansion of TPH and BDN cells might reflect the autoimmune response present in the joints of ANA+ JIA patients.

研究目的：抗核抗体（antinuclear antibody, ANA）阳性的幼年特发性关节炎（Juvenile Idiopathic Arthritis, JIA）以滑膜B细胞过度活化为特征，但CD4+ T细胞在促进局部B细胞活化中的确切作用尚不明确。本研究旨在阐明JIA中介导异常B细胞活化的滑膜CD4+ T细胞的表型与功能。
研究方法：采用流式细胞术比较滑膜液（synovial fluid, SF）中PD-1（programmed cell death 1）高表达（PD-1hi）CD4+ T细胞与扁桃体滤泡辅助性T细胞（follicular helper T, TFH）的表型及细胞因子谱；应用TCRVB下一代测序技术分析T细胞亚群的克隆扩增迹象；通过体外共培养实验解析此类T细胞亚群对B细胞的功能影响。
研究结果：多维度流式细胞术分析显示，在ANA阳性JIA患者的关节腔中，共表达白细胞介素-21（interleukin-21, IL-21）与干扰素-γ（interferon-γ, IFN-γ）的PD-1hiCXCR5（CXC chemokine receptor 5）-HLA-DR（human leukocyte antigen DR）+ CD4+ T细胞发生扩增并蓄积。此类T细胞呈现克隆扩增特征，其T细胞受体克隆型具有限制性；表型上类似外周辅助性T细胞（peripheral T helper, TPH），具有滤泡外趋化因子受体表达模式，高表达T-bet与Blimp-1，但Bcl-6表达水平较低。体外实验证实，滑膜液中的TPH细胞可通过分泌IL-21与IFN-γ，将B细胞分化定向诱导为CD21（cluster of differentiation 21）lo/-CD11c（cluster of differentiation 11c）+表型；且该类细胞与滑膜液中CD21lo/-CD11c+CD27（cluster of differentiation 27）-IgM（immunoglobulin M）-双阴性B细胞（double-negative B cells, BDN）的原位出现呈相关性。
研究结论：克隆扩增的CD4+ TPH细胞在ANA阳性JIA患者的关节腔中蓄积，可特异性促进CD21lo/-CD11c+BDN细胞的分化。TPH细胞与BDN细胞的扩增或可反映ANA阳性JIA患者关节腔内的自身免疫应答状态。