Abstract： Objective:To observe the changes of peripheral blood T cell subsets and serum tumor necrosis factor (TNF)-α and interleukin (IL)-6 contents in narcolepsy type 1 (NT1) patients and their correlations with narcolepsy, and provide basis for finding the biological markers of narcolepsy.Methods:A retrospective analysis was performed. From March 2022 to December 2023, 23 patients with NT1 admitted to Epilepsy and Sleep Disorder Center, Second Affiliated Hospital of Harbin Medical University and 23 healthy controls underwent physical examination of nervous system in our center were enrolled. T lymphocyte subsets CD4 + and CD8 + in peripheral blood were calculated by flow cytometry. Serum TNF-α and IL-6 contents were detected by enzyme-linked immunosorbent assay. Multivariate Logistic regression was used to determine the correlations of NT1 with CD4 + T lymphocyte count and IL-6 and TNF-α contents, and diagnostic values of CD4 + T lymphocyte and TNF-α in NT1 were evaluated via area under receiver operating characteristics (ROC) curve. Results:Compared with the healthy controls, the NT1 patients had significantly increased peripheral blood CD4 + T lymphocyte count ([820.61±316.87] /μL vs. [1121.04±387.47] /μL), and significantly higher serum TNF-α and IL-6 contents ([39.97±10.64] pg/mL vs. [57.01±19.92] pg/mL; [22.50±6.09] pg/mL vs. [33.66±17.28] pg/mL, P<0.05). No significant difference in peripheral blood CD8 + T lymphocyte count was noted between the 2 groups ([668.65±276.45] pg/mL vs. [592.52±217.78] pg/mL, P>0.05). Multivariate Logistic regression showed that CD4 + T lymphocyte count and serum TNF-α content were independent risk factors for NT1 ( OR=1.004, 95% CI: 1.001-1.006, P=0.007; OR=1.133, 95% CI: 1.032-1.243, P=0.009). Area under ROC curve of the two combined indexes was 0.881(95% CI: 0.784-0.977, P=0.001), enjoying sensitivity of 0.783 and specificity of 0.870. Conclusion:Combination of peripheral blood CD4 + T lymphocyte count and serum TNF-α content has high diagnostic performance in predicting NT1.