The presence of pre-existing malignancy in murine hosts results in increased immune dysregulation and risk of mortality following a septic insult. Based on the known systemic immunologic changes that occur in cancer hosts, we hypothesized that the presence of pre-existing malignancy would result in phenotypic and functional changes in CD4⁺ T cell responses following sepsis. In order to conduct a non-biased, unsupervised analysis of phenotypic differences between CD4⁺ T cell compartments, cohorts of mice were injected with LLC1 tumor cells and tumors were allowed to grow for 3 weeks. These cancer hosts and age-matched non-cancer controls were then subjected to CLP. Splenocytes were harvested at 24h post CLP and flow cytometry and SPADE (Spanning-tree Progression Analysis of Density-normalized Events) were used to analyze populations of CD4⁺ cells most different between the two groups. Results indicated that relative to non-cancer controls, cancer mice contained more resting memory CD4⁺ T cells, more activated CD4⁺ effectors, and fewer naïve CD4⁺ T cells during sepsis, suggesting that the CD4⁺ T cell compartment in cancer septic hosts is one of increased activation and differentiation. Moreover, cancer septic animals exhibited expansion of two distinct subsets of CD4⁺ T cells relative to previously healthy septic controls. Specifically, we identified increases in both a PD-1^hi population and a distinct 2B4^hi BTLA^hi LAG-3^hi population in cancer septic animals. By combining phenotypic analysis of exhaustion markers with functional analysis of cytokine production, we found that PD-1⁺ CD4⁺ cells in cancer hosts failed to make any cytokines following CLP, while the 2B4⁺ PD-1^lo cells in cancer mice secreted increased TNF during sepsis. In sum, the immunophenotypic landscape of cancer septic animals is characterized by both increased CD4⁺ T cell activation and exhaustion, findings that may underlie the observed increased mortality in mice with pre-existing malignancy following sepsis.

鼠宿主中先前存在的恶性肿瘤导致感染性感染后免疫失调增加和死亡风险增加。基于在癌症宿主中发生的已知的全身免疫学变化，我们假设先前存在的恶性肿瘤的存在将导致败血症后CD4 ⁺ T细胞反应的表型和功能变化。为了对CD4 ⁺之间的表型差异进行无偏见，无监督的分析在T细胞区室中，向一批小鼠注射LLC1肿瘤细胞，并使肿瘤生长3周。然后将这些癌症宿主和与年龄匹配的非癌症对照进行CLP。在CLP后24小时收集脾细胞，并使用流式细胞仪和SPADE（密度标准化事件的生成树进展分析）分析两组之间差异最大的CD4 ⁺细胞群体。结果表明，相对于非癌症对照，癌症小鼠在脓毒症期间包含更多的静息记忆CD4 ⁺ T细胞，更多的活化CD4 ⁺效应子和较少的幼稚CD4 ⁺ T细胞，这表明CD4 ⁺癌症败血症宿主中的T细胞区室是增加的活化和分化之一。此外，相对于先前健康的脓毒症对照，脓毒症动物表现出CD4 ⁺ T细胞两个不同亚群的扩增。具体来说，我们确定了败血症动物中PD-1 ^hi群体和2B4 ^hi BTLA ^hi LAG-3 ^hi群体的增加。通过将衰竭标志物的表型分析与细胞因子产生的功能分析相结合，我们发现癌症宿主中的PD-1 ⁺ CD4 ⁺细胞在CLP后不能产生任何细胞因子，而2B4 ⁺ PD-1 ^lo败血症过程中，癌症小鼠体内的TNF-α细胞分泌的TNF增加。总而言之，癌症败血症动物的免疫表型态的特征是CD4 ⁺ T细胞活化和衰竭能力增加，这可能是脓毒症后已有恶性肿瘤的小鼠观察到的死亡率增加的基础。