Analysis of tumor cell death on antigen-specific immune responses

肿瘤细胞死亡的方式被认为对适应性免疫反应的产生有重大影响。在我们之前的研究中，我们已经能够证明，在皮下生长的肿瘤中，诱导凋亡和坏死对肿瘤特异性CD8+T细胞具有截然不同的影响。而凋亡性肿瘤细胞死亡促进抗肿瘤免疫反应，而坏死性肿瘤细胞死亡则削弱这些反应。2012年，我们已经能够研究在没有病原体相关分子模式(PAMPs)的无菌条件下，坏死细胞如何影响抗原特异性CD8+T细胞介导的适应性免疫反应的诱导。我们在体外和体内检测了抗原特异性CD8+T细胞对原代无菌坏死性肿瘤细胞的反应。我们发现，原代坏死细胞本身不能产生CD8+T细胞依赖的针对细胞相关抗原的免疫反应。我们发现，只有在PAMPs或类似物存在的情况下，坏死细胞才能触发CD8+T细胞免疫，例如p(Di-DC)和/或未甲基化的CpG DNA。在坏死诱导之前，这些PAMP电穿孔肿瘤细胞，通过TLR9/MyD88依赖的途径触发抗原特异性CD8+T细胞反应。此外，我们发现，即使在非无菌条件下，坏死细胞也含有能够阻止CD8+T细胞交叉启动的因子，这可能是免疫抑制的一种机制。这些结果表明，在PAMPs存在的情况下，可以诱导抗原特异性的CD8+T细胞对原代坏死性肿瘤细胞的反应，从而对抗肿瘤疫苗策略的发展产生实质性的影响。

The way in which tumor cells die is proposed to have a substantial impact on the generation of adaptive immune responses. In our previous studies we have been able to demonstrate that induction of apoptosis versus necrosis in subcutaneously growing tumors has profoundly different effects on tumor specific CD8+ T cells. While apoptotic tumor cell death promote anti-tumor immune responses necrotic tumor cell death impair these responses. In 2012 we have been able to study how necrotic cells influence the induction of antigen-specific CD8+ T cell-mediated adaptive immune responses under sterile conditions, in the absence of pathogen associated molecular patterns (PAMPs). We examined antigen-specific CD8+ T cell responses to primary sterile necrotic tumor cells both in vitro and in vivo. We found that primary necrotic cells alone fail to generate CD8+ T cell-dependent immune responses toward cell-associated antigens. We show that necrotic cells trigger CD8+ T-cell immunity only in the presence of PAMPs or analogs, such as p(dI-dC) and/or unmethylated CpG DNA. The electroporation of tumor cells with these PAMPs prior to necrosis induction triggered antigen-specific CD8+ T-cell responses through a TLR9/MyD88-dependent pathway. In addition, we found that necrotic cells contain factors that can block the cross-priming of CD8+ T cells even under non-sterile conditions and can serve as a possible mechanism of immunosuppression. These results suggest that antigen-specific CD8+ T-cell responses to primary necrotic tumor cells can be induced in the presence of PAMPs and thus have a substantial impact on the development of antitumor vaccination strategies.