Transcranial magnetic stimulation (TMS) can activate discrete areas of the cerebral cortex through the intact skull of healthy conscious volunteers. A magnetic coil generates a brief and focused magnetic field that penetrates the skull to activate the specific area of cerebral cortex beneath. This non-invasive procedure is painless, well tolerated by participants and now widely used to explore brain function. We used TMS to investigate asymmetrical cortical regulatory influences on one aspect of immune function: secretion of the antibody immunoglobulin A (S-IgA) into saliva. The right and left temporo-parietal-occipital cortex of 16 healthy, conscious subjects was stimulated on two different occasions, at least 1 week apart. There was an immediate increase in S-IgA concentration following both right and left stimulation. Saliva volume was reduced immediately post-right but not left stimulation. When secretion (microg/min) of S-IgA was calculated (controlling for changing saliva volume) an increase was apparent following left but not right hemisphere stimulation. Furthermore, a significant difference between the relationship between S-IgA concentration and volume of saliva post-left and right stimulation was observed. We conclude that TMS can be used as a tool to investigate cortical regulation of autonomic and immune function in healthy, conscious human subjects and that secretion of saliva and S-IgA is differentially affected by stimulation of the left and right cerebral cortex.

Secretory immunoglobulin A (sIgA) measured in saliva, an index of mucosal immunity, has repeatedly been shown to be sensitive to psychological variables. Chronic stress is downregulatory whereas an acute psychological challenge induces mobilisation. We examined whether an acute manipulation of mood to induce negative hedonic tone would be downregulatory, as in the chronic stress paradigm and further, whether induction of positive mood might have opposite effects. Two separate experiments were conducted. In the first, mood manipulation was by mental recall and in the second by music. For both sIgA concentration and sIgA secretion rate there was a significant elevation in response to the mood manipulation by recall regardless of hedonic tone. There was some evidence that for sIgA secretion rate the response was more pronounced for positive mood. Mood induction by music also resulted in significant elevations in sIgA concentration and secretion rate and responses were not distinguished by mood valence. None of the mood induction procedures was associated with changes in free cortisol. In these studies, we found no evidence that transient lowering of mood was downregulatory for salivary sIgA. The predominant finding was of sIgA mobilisation.

There have been very few reports addressing levels and distribution of commonly used PNI measures in large community samples. In this study, we report such data for secretion rates of secretory immunoglobulin A (sIgA), as determined from saliva samples taken from 1971 subjects interviewed as part of the West of Scotland Twenty-07 survey of health in West Central Scotland. Univariate analyses of demographic variables found lower sIgA and salivary flow to be significantly related to poorer social class, increased age, and being female. Smokers also had lower sIgA but not lower salivary flow. Multivariate analysis showed that demographic variables were significant predictors of sIgA independently of each other and assay variation. Adding smoking status to the equation confirmed it as an independent predictor and also indicated that social class differences in sIgA are partly explicable in terms of smoking status. In view of reported associations between sIgA levels and stress, its role as a first line of mucosal defense, and its relevance to health, these first results from a large survey are of interest. Further work is now needed to explore which factors, including psychosocial ones, may be contributing to subgroup differences.