Human CCR6+ Th cells show both an extended stable gradient of Th17 activity and imprinted plasticity [Spsingh-10xTCR-CMV]

Th17 cells have been investigated in mice primarily for their contributions to autoimmune diseases. However, the pathways of differentiation of Th17 and related Th cells (type 17 cells) and the structure of the type 17 memory population in humans are not well understood; such understanding is critical for manipulating these cells in vivo. By exploiting differences in levels of surface CCR6, we found that human type 17 memory cells, including individual T cell clonotypes, form an elongated continuum of type 17 character along which cells can be driven by increasing RORt. This continuum includes cells preserved within the memory pool with potentials that reflect the early preferential activation of multiple over single lineages. The CCR6+ cells’ phenotypes and epigenomes are stable across cell divisions under homeostatic-like conditions. Nonetheless, activation in polarizing and non-polarizing conditions can yield additional functionalities, revealing, respectively, both environmentally induced and imprinted mechanisms that contribute differentially across the continuum to yield the unusual plasticity ascribed to type 17 cells. Single cell TCR V-d-J sequencing of 4 T-cell subsets with graded levels of CCR6. Independent replicates from two donors. This experiment utilizes an enrichment of an anti-CMV sub-population of T-cells ,which decreases the TCR diversity such that shared clonotypes can be detected and tracked across the CCR6 subsets.

Th17细胞（Th17 cells）最初在小鼠模型中被广泛研究，其核心研究方向为该细胞在自身免疫病中的致病作用。然而，目前学界对人类体内Th17细胞及相关17型T辅助细胞（type 17 cells）的分化通路，以及人类17型记忆T细胞群体的结构特征仍缺乏充分认知；而这类认知对于在活体中精准调控此类细胞至关重要。
研究人员借助表面CCR6表达水平的差异，发现人类17型记忆T细胞（包括单个T细胞克隆型）形成了一条连续的Th17特性梯度轴：随着RORγt（维甲酸相关孤儿受体γt）表达水平升高，细胞的Th17特性可被逐步强化。该梯度轴包含留存于记忆细胞库中的细胞亚群，其潜能特性反映了多谱系激活相较于单谱系激活的早期优先性。
在稳态样培养条件下，CCR6阳性细胞的表型与表观基因组在细胞分裂过程中始终保持稳定。尽管如此，在极化与非极化培养条件下的细胞激活可赋予其额外的功能特性，分别揭示了环境诱导机制与表观遗传印记机制——这两类机制在该梯度轴上发挥差异化作用，共同造就了Th17型细胞所特有的独特可塑性。
本实验针对4个CCR6表达水平呈梯度差异的T细胞亚群开展了单细胞TCR V(D)J测序，实验采用两名健康供体的独立重复样本。本实验通过富集抗巨细胞病毒（CMV）T细胞亚群以降低TCR多样性，从而能够在不同CCR6亚群中检测并追踪共享的T细胞克隆型。