Sugiyarto Gessa, Prossor David, Dadas Osman, Arcia-Anaya E David, Elliott Tim, James Edward
Centre for Cancer Immunology, School of Cancer Sciences, University of Southampton Faculty of Medicine, University Hospital Southampton, Southampton, UK.
Institute for Life sciences, University of Southampton, Southampton, UK.
Immunother Adv. 2020 Nov 25;1(1):ltaa001. doi: 10.1093/immadv/ltaa001. eCollection 2021 Jan.
Regulatory T cells (Treg) play a major role in the suppression of protective anti-tumour T cell responses. In the CT26 BALB/c murine model of colorectal carcinoma, Tregs differentially suppress responses to two characterised CD8+ T epitopes, AH1 and GSW11, which results in an absence of detectable IFN-γ-producing GSW11-specific T cells in the spleen and lymph nodes of tumour challenged mice. Activation of GSW11-specific T cells correlates with protection against tumour progression. We wanted to examine the presence of non-functional GSW11-specific T cells in Treg replete and depleted mice, assess their phenotype and their affinity compared to AH1-specific T cells.
We used peptide-specific tetramers to identify tumour-specific CD8+ T cells and assessed the cell surface expression of markers associated with exhaustion (PD-1, Tim3 and Lag-3) and their function by IFN-g production using flow cytometry. We also assessed the T cell receptor (TcR) clonality of tumour-specific T cells. Tetramer competition assays were performed to determine the relative affinity of identified TcR.
Here, we show that GSW11-specific T cells are in fact induced in Treg-replete, CT26-bearing mice, where they make up the majority of tumour-infiltrating CD8+ lymphocytes, but exhibit an 'exhausted' phenotype. This dysfunctional phenotype is induced early in the anti-tumour response in tumours. Depletion of Tregs prior to tumour challenge correlates with an altered T cell receptor (TcR) repertoire. Moreover, the avidity of GSW11-specific TcRs that expanded in the absence of Tregs was significantly lower compared with TcRs of CD8+populations that were diminished in protective anti-tumour responses.
Our results indicate that Tregs suppress the induction of protective anti-tumour T cell responses and may signify that low-avidity T cells play an important role in this protection.
调节性T细胞（Treg）在抑制保护性抗肿瘤T细胞反应中起主要作用。在CT26 BALB/c小鼠结直肠癌模型中，Tregs对两种已鉴定的CD8 + T细胞表位AH1和GSW11的反应有差异地抑制，这导致在肿瘤攻击小鼠的脾脏和淋巴结中缺乏可检测到的产生IFN-γ的GSW11特异性T细胞。GSW11特异性T细胞的激活与抗肿瘤进展的保护相关。我们想检查在Treg充足和缺失的小鼠中是否存在无功能的GSW11特异性T细胞，评估它们的表型以及与AH1特异性T细胞相比的亲和力。
我们使用肽特异性四聚体来鉴定肿瘤特异性CD8 + T细胞，并通过流式细胞术评估与耗竭相关的标志物（PD-1、Tim3和Lag-3）的细胞表面表达及其通过IFN-γ产生的功能。我们还评估了肿瘤特异性T细胞的T细胞受体（TcR）克隆性。进行四聚体竞争试验以确定鉴定的TcR的相对亲和力。
在这里，我们表明在Treg充足的荷CT26小鼠中实际上诱导了GSW11特异性T细胞，它们构成了肿瘤浸润CD8 +淋巴细胞的大多数，但表现出“耗竭”表型。这种功能失调的表型在肿瘤的抗肿瘤反应早期就被诱导。在肿瘤攻击前耗尽Tregs与T细胞受体（TcR）库的改变相关。此外，与在保护性抗肿瘤反应中减少的CD8 +群体的TcR相比，在没有Tregs的情况下扩增的GSW11特异性TcR的亲和力明显更低。
我们的结果表明，Tregs抑制保护性抗肿瘤T细胞反应的诱导，这可能意味着低亲和力T细胞在这种保护中起重要作用。
