Salivary lysozyme: a noninvasive marker for the study of the effects of stress of natural immunity.

Salivary lysozyme levels were measured to determine the effect of stress on innate mucosal immunity. In the first study perceived stress levels of 39 participants were using a stress/arousal checklist questionnaire. Salivary lysozyme levels were found to show a negative correlation (r = -.477, p < .01) with the perceived stress level. In a second study, salivary lysozyme concentrations were measured during periods of high and low stress in the form of an actual stressor--final year examinations. The concentration of lysozyme was found to be significantly (p < .05) lower in the sample taken before the examination when the students were awaiting entry into the examination hall compared to the levels after completion of all examinations. These results indicate that salivary lysozyme concentrations are sensitive to psychological stress and could be utilized as a potential marker in studies looking at the effects of stress on immunity. Because the usefulness of sIgA as a marker has been questioned, the use of salivary lysozyme as a noninvasive index of mucosal immunity warrants further investigation.