Positive correlations between salivary biomarkers of stress and mucosal immunity

Published research would suggest that psychological stress results in high levels of cortisol in the blood and saliva, and that high levels of such stress would result in lowered levels of immunity (a negative correlation). To begin exploring the relationships between psychological stress and mucosal immunity, this study examined the levels of various biomarkers in the saliva. As part of a larger survey of occupational stress, timed, whole, unstimulated saliva was collected from 16 male staff working at an Australian university on two consecutive mornings. Secretory IgA (S-IgA), lysozyme (S-Lys), albumin (S-Alb) and cortisol (S-Cort) concentrations in saliva were assessed by immunoassay. These were then converted to secretion rates per minute by taking account of the volume and time for saliva collection. Correlations between levels of the various biomarkers were assessed by the non-parametric Spearman’s Rank Correlation test (n ÂŒ 32). There were significant, bivariate correlations between salivary secretion rates of all of the biomarkers examined: S-IgA, S-Lys, S-Cort and S-Alb. The direction of correlation in all cases was positive. For example, high secretion rates of cortisol were correlated with high secretion rates of lysozyme (r ÂŒ 0.518) and IgA (r ÂŒ 0.668). These results showing positive correlations were surprising, indicating high levels of mucosal immunity correlated with high levels of cortisol secretion. The subjects in the study were possibly suffering chronic psychological stress, supported by results of an occupational stress survey carried out at the same time. These findings could represent an adaptation to long-term, high levels of psychological strain in these subjects, such that their mucosal immunity is able to stay relatively high. Clearly additional work, with larger subject numbers, is required to further examine the usefulness of salivary biomarkers in studies investigating the links between stress and mucosal immunity