Reference intervals for plasma IFN-α, TNF-α, IL-12p70, and IFN-γ by flow cytometry in healthy adults from eastern China: a single-center study.

Background: Cytokines are essential regulators of immune homeostasis and play critical roles in both physiological immune modulation and pathological inflammatory processes. In this study, flow cytometry was applied to quantify plasma levels of interferon-α (IFN-α), tumor necrosis factor-α (TNF-α), interleukin-12p70 (IL-12p70), and interferon-γ (IFN-γ), aiming to establish reference intervals that may support clinical disease assessment and therapeutic decision-making. Methods: Between July and November 2025, 728 healthy adults from eastern China's Jiangsu region were enrolled as reference subjects based on predefined eligibility criteria. Plasma levels of IFN-α, TNF-α, IL-12p70, and IFN-γ were measured via flow cytometry. The Kolmogorov-Smirnov test was used to evaluate data normality. Following the CLSI C28-A3 and WS/T 402-2024 guidelines, reference intervals for the four plasma cytokines in the overall population were derived using a nonparametric method covering the 2.5th-97.5th percentile range. Results: Plasma concentrations of four cytokines demonstrated non-Gaussian distributions. No significant differences were observed between sexes or among age groups (all P > 0.05), allowing combined analysis across all participants. The established reference intervals were as follows: IFN-α: 0.13-5.81 pg/mL, TNF-α: 0.60-4.89 pg/mL, IL-12p70: 0.24-5.44 pg/mL, and IFN-γ: 0.50-6.88 pg/mL. Conclusions: This study established flow cytometry-based reference intervals for plasma IFN-α, TNF-α, IL-12p70, and IFN-γ in healthy adults from Jiangsu Province, eastern China. These intervals provide a reliable reference for assessing immune status, guiding the management of immune-related diseases, and supporting laboratories in the adoption or establishment of reference intervals.