Seasonal changes in secretory immunity indices in saliva in indigenous and alien inhabitants of the Yakutia Arctic zone

Abstract

Introduction. The combination of extreme climate with intensive migration processes creates favourable conditions for the spread of infectious diseases in the Arctic zone of the Russian Federation. The purpose of the study: comparative analysis of immunity indicators in saliva samples of indigenous and alien residents of Yakutia Arctic zone, taking into account the influence of seasonal factors. Materials and methods. Samples of mixed saliva of indigenous (n=212) and alien (n=120) male residents from Chokurdakh and Tiksi settlements were taken in 4 batches corresponding to the seasonal transition from summer to early winter. Levels of secretory IgA (sIgA) and cytokines IL-1ß, IL-8 and IL-6 in saliva were determined by ELISA. Main Effects ANOVA was used for the data analysis. Results. No significant age-related changes of the indicators were found. During the transition from summer to winter, there was a decrease in sIgA, IL-1ß, and IL-8 levels in saliva of the examined persons (p from 0.001 to 1.6•10–7). Rate of seasonal changes did not differ between indigenous and alien inhabitants. IL-6 level in saliva of Chokurdakh residents (200 km from the sea) was higher (F(1,139)=9,202; p=0.003) and sIgA level was lower (F(1,324)=3,560; p=0.060) than corresponding levels in residents of coastal settlement Tiksi. Comparison of the body mass indices (medians 24.3 in Chokurdakh and 26.2 in Tiksi, p=0.0005) confirms that it may be the result of inequality in physical activity of residents due to almost 2-fold increase in wind speed and precipitation in Tiksi. Limitations. Monitoring period till the beginning of winter, and not later, could predetermine the absence of the expected differences between indigenous (evolutionarily adapted) and alien residents. Conclusion. Evaluation of immunity indicators in saliva samples is a simple and informative approach to study mechanisms of human adaptation to extreme climatic conditions.