Predictive value of PD-1⁺CD3⁺ T cells for 30-day mortality in patients with sepsis

Increased expression of programmed cell death protein-1 (PD-1) on T lymphocyte subsets is associated with sepsis immunosuppression and offers potential biomarkers for prognosis. However, few studies have assessed the effect of PD-1 expression on CD3⁺ T lymphocytes in predicting sepsis. The aim of this study was to investigate the relationship between PD-1 expression on CD3⁺ T lymphocytes and 30-day mortality in patients with sepsis. A total of 180 patients with sepsis, comprising 117 survivors and 63 non-survivors, were included in the analysis. Lymphocyte counts and PD-1 expression on T lymphocytes were quantified in peripheral blood samples through the application of flow cytometry. Regression models, receiver-operating characteristic curves (ROC) and reclassification analyses were performed to assess the relationship between the biomarkers under investigation and 30-day mortality. Results showed the level of PD-1 expressing CD3⁺ T cells was obviously increased in the non-survivor group compared with the group that survived (P < 0.05). Based on multiple logistic regression analysis, PD-1⁺CD3⁺T cells (OR = 1.02, P < 0.05), SOFA score (OR = 1.20, P < 0.05) and APACHE II score (OR = 1.14, P < 0.05) were independent risk factors for mortality of sepsis. PD-1⁺CD3⁺ T cells showed an area under the curve(AUC) of 0.623(95% CI, 0.534-0.713) in predicting sepsis mortality. AUCs for SOFA and APACHE II scores were 0.706 (95% CI, 0.624-0.789) and 0.784 (95% CI, 0.714-0.854), respectively. Adding PD-1⁺CD3⁺ T cells to the SOFA and APACHE II scoring systems significantly improved predictive accuracy, with an AUC enhancement and a top Youden's index of 0.553. The Cox regression analysis revealed significantly lower 30-day survival rates in patients with high PD-1 expressing CD3⁺ T cells (> 36.56%). PD-1 expression on CD3⁺T lymphocytes can serve as a promising prognostic biomarker in sepsis patients, enhancing the predictive accuracy of APACHE II and SOFA scores.