Altered thymic differentiation and modulation of arthritis by invariant NKT cells expressing mutant ZAP70 [RNA-Seq]

Various subsets of invariant natural killer T (iNKT) cells with different cytokine productions develop in the mouse thymus, but the factors driving their differentiation remain unclear. Here we show that hypomorphic alleles of Zap70 or chemical inhibition of Zap70 catalysis lead to an increase of IFN-g-producing iNKT cells (NKT1 cells), suggesting NKT1 cells may require a lower TCR signal threshold. Zap70 mutant mice develop IL-17-dependent arthritis. iNKT cells and therapeutic induction of IFN-g secretion by activating iNKT cells are protective in this model, but the representation of IFNg versus IL-17 secreting iNKT cells in the joint change in favor of IL-17 producers as disease worsened. NKT1 cells are also present in the synovial fluid of arthritis patients, where they could be beneficial. Our data therefore suggest that TCR signal strength during thymic differentiation may influence not only IFNg production, but also the protective function of iNKT cells in arthritis. Overall design: Three subsets of iNKT cells from the thymi of WT control and SKG mice were analyzed. Three independent experiments were carried out. Triplicates of each sample were analyzed分泌不同细胞因子的各类恒定自然杀伤T细胞（invariant natural killer T, iNKT）亚群可在小鼠胸腺中发育，但调控其分化的具体分子机制仍未明确。本研究显示，ZAP70的低功能等位基因突变或通过化学手段抑制ZAP70的催化活性，均可使分泌干扰素-γ（interferon-gamma, IFN-γ）的iNKT细胞（即NKT1细胞）的比例升高，提示NKT1细胞可能需要更低的T细胞受体（T cell receptor, TCR）信号阈值。ZAP70突变小鼠可发生白细胞介素17（interleukin-17, IL-17）依赖性关节炎。通过激活iNKT细胞以治疗性诱导IFN-γ分泌的策略在该疾病模型中具有保护作用，但随着病情恶化，关节腔内分泌IFN-γ与分泌IL-17的iNKT细胞的比例会向分泌IL-17的细胞群体倾斜。关节炎患者的滑液中也存在NKT1细胞，这类细胞或可发挥有益作用。综上，本研究数据表明，胸腺分化阶段的TCR信号强度不仅可影响iNKT细胞的IFN-γ分泌能力，还可调控其在关节炎中的保护功能。实验设计：本研究分析了野生型（wild type, WT）对照小鼠与SKG小鼠胸腺中的三类iNKT细胞亚群，共开展3次独立实验，每份样本均设置3次重复。