Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany.
Department of Veterinary Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States.
Front Immunol. 2024 Aug 9;15:1439213. doi: 10.3389/fimmu.2024.1439213. eCollection 2024.
Conventional CD4 regulatory T (Treg) cells characterized by expression of the key transcription factor forkhead box P3 (FoxP3) are crucial to control immune responses, thereby maintaining homeostasis and self-tolerance. Within the substantial population of non-conventional T cell receptor (TCR)αβ CD4CD8α double-negative (dn) T cells of dogs, a novel FoxP3 Treg-like subset was described that, similar to conventional CD4 Treg cells, is characterized by high expression of CD25. Noteworthy, human and murine TCRαβ regulatory dn T cells lack FoxP3. Immunosuppressive capacity of canine dn T cells was hypothesized based on expression of inhibitory molecules (interleukin (IL)-10, . Here, to verify their regulatory function, the dnCD25 (enriched for FoxP3 Treg-like cells) and the dnCD25 fraction, were isolated by fluorescence-activated cell sorting from peripheral blood mononuclear cells (PBMC) of Beagle dogs and analyzed in an suppression assay in comparison to conventional CD4CD25 Treg cells (positive control) and CD4CD25 T cells (negative control). Canine dnCD25 T cells suppressed the Concanavalin A-driven proliferation of responder PBMC to a similar extent as conventional CD4CD25 Treg cells. Albeit to a lesser extent than FoxP3-enriched dn and CD4CD25 populations, even dnCD25 T cells reduced the proliferation of responder cells. This is remarkable, as dnCD25 T cells have a FoxP3 phenotype comparable to non-suppressive CD4CD25 T cells. Both, CD25 and CD25 dn T cells, can mediate suppression independent of cell-cell contact and do not require additional signals from CD4CD25 T cells to secrete inhibitory factors in contrast to CD4CD25 T cells. Neutralization of IL-10 completely abrogated the suppression by dnCD25 and CD4CD25 Treg cells in a Transwell™ system, while it only partially reduced suppression by dnCD25 T cells. Taken together, unique canine non-conventional dnCD25 FoxP3 Treg-like cells are potent suppressor cells . Moreover, inhibition of proliferation of responder T cells by the dnCD25 fraction indicates suppressive function of a subset of dn T cells even in the absence of FoxP3. The identification of unique immunoregulatory non-conventional dn T cell subpopulations of the dog is of high relevance, given the immunotherapeutic potential of manipulating regulatory T cell responses
常规 CD4 调节性 T (Treg) 细胞的特征是表达关键转录因子叉头框 P3 (FoxP3)，对于控制免疫反应至关重要，从而维持体内平衡和自身耐受。在狗的大量非常规 T 细胞受体 (TCR)αβ CD4CD8α 双阴性 (dn) T 细胞群体中，描述了一种新型 FoxP3 Treg 样亚群，类似于常规 CD4 Treg 细胞，其特征是高表达 CD25。值得注意的是，人和鼠 TCRαβ 调节性 dn T 细胞缺乏 FoxP3。根据抑制分子 (白细胞介素 (IL)-10、 的表达，假设犬 dn T 细胞具有免疫抑制能力。在这里，为了验证它们的调节功能，通过荧光激活细胞分选从比格犬外周血单核细胞 (PBMC) 中分离出 dnCD25(富含 FoxP3 Treg 样细胞)和 dnCD25 部分，并在与常规 CD4CD25 Treg 细胞 (阳性对照) 和 CD4CD25 T 细胞 (阴性对照) 的抑制测定中进行分析。与常规 CD4CD25 Treg 细胞相似，犬 dnCD25 T 细胞抑制 Concanavalin A 驱动的反应性 PBMC 增殖。尽管不如 FoxP3 富集的 dn 和 CD4CD25 群体明显，但即使 dnCD25 T 细胞也减少了反应性细胞的增殖。这很了不起，因为 dnCD25 T 细胞具有与非抑制性 CD4CD25 T 细胞相当的 FoxP3 表型。dnCD25 T 细胞和 CD25 dn T 细胞都可以独立于细胞-细胞接触进行抑制，并且与 CD4CD25 T 细胞不同，它们不需要来自 CD4CD25 T 细胞的额外信号来分泌抑制因子。在 Transwell™系统中，中和 IL-10 完全消除了 dnCD25 和 CD4CD25 Treg 细胞的抑制作用，而仅部分降低了 dnCD25 T 细胞的抑制作用。总之，犬类独特的非常规 dnCD25 FoxP3 Treg 样细胞是强大的抑制细胞。此外，dnCD25 部分抑制反应性 T 细胞的增殖表明 dn T 细胞亚群即使在缺乏 FoxP3 的情况下也具有抑制功能。鉴于操纵调节性 T 细胞反应的免疫治疗潜力，鉴定犬的独特免疫调节性非常规 dn T 细胞亚群具有高度相关性。
