The relationship between salivary secretory immunoglobulin A and cortisol:neuroendocrine response to awakening and the diurnal cycle

The level of secretory immunoglobulin A (sIgA) measured in saliva is downre gulated during periods of chronic stress. In contrast, the response to an a cute stress challenge is a transient increase. The process of awakening is associated with stress neuroendocrine activation characterised by increases in salivary cortisol. We therefore examined if this period of hypothalamic -pituitary-adrenal (HPA) activation was associated with changes in salivary sIgA. Associations of sIgA with the diurnal cortisol cycle were also inves tigated in a separate study. The awakening cortisol response was measured i n 30 healthy day-active young adults. There was a marked elevation from the first awakening level over the succeeding 30 min. SIgA showed the opposite response with a marked fall from the highest first awakening concentration in the same samples over the same period. The cortisol rise was significan tly correlated with the sIgA fall (r = 0.42). Salivary sIgA showed a simila r diurnal cycle to cortisol in a study on eight healthy young adults. An ea rly morning acrophase was followed by a decline to a stable base some 6 h a fter awakening. The physiological significance of these relationships and p ossible implications for vulnerability to infection are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.