Environmental modulation of cytokine profiles in European bison (Bison bonasus): implications for ecoimmunological monitoring and conservation health

Understanding immune biomarkers in wildlife may improve disease surveillance. The European bison ( Bison bonasus ), Europe’s largest terrestrial mammal, remains vulnerable to infectious diseases and environmental stressors despite successful restitution from near extinction. However, little is known about cytokine-mediated immune responses in this species and their relationship with pathological burden and environmental conditions. This study characterized circulating cytokine profiles in free-ranging and captive European bison populations in Poland within an ecoimmunological framework. Serum concentrations of IL-6, IL-8, IL-10, TNF-α, IFN-γ, IL-1β, and IL-4 were evaluated in relation to age, season, sanitary status, population type, latitude and tuberculosis status. Multivariable analyses demonstrated cytokine-specific associations with temporal, demographic, sanitary, geographical, and population-related factors. Serum IL-6 level showed significant monthly variation and was associated with geographical region and population type, whereas IL-8 was associated with month and sanitary status. IL-10 and TNF-α decreased significantly with increasing age and showed temporal variation. IFN-γ also decreased significantly with age and was independently associated with month, sex, sanitary status, and geographical region, whereas no independent association with population type was detected. Several associations identified in univariable comparisons were attenuated or no longer significant after adjustment for covariates. In the TB diagnostic analysis, IFN-γ showed the strongest discriminatory performance (AUC = 0.800), followed by IL-6 (AUC = 0.718). An IFN-γ threshold of ≥ 750 pg/ml yielded 76.9% sensitivity and 80.0% specificity. Applying a sequential conjunction rule of IFN-γ ≥ 750 pg/ml and IL-6 > 240 pg/ml increased positive predictive value to 88.9%. These findings suggest that cytokine profiling provide valuable insight into immune regulation, health status, and disease surveillance in European bison and may support the development of supporting immunodiagnostic tools for wildlife conservation and One Health monitoring.