Nasal secretory IgA circadian rhythm: a single-dose suppression test.

The existence of a clear circadian rhythm in the local secretion of nasal IgA is a well-known phenomenon which is confirmed in the present research. Since the temporal pattern of secretory IgA (SIgA) strictly parallels the ACTH-cortisol cycle, a dependence was hypothesized in previous research, but the suppression of adrenal rhythm by means of massive doses of exogenous corticosteroids showed no influence on the SIgA cycle. In the present research a more sophisticated method of corticoid-incretion suppression was used; the single-dose suppression test with dexamethasone, which influences only the impulsive phase of the rhythm. In this case too, however, no influence was demonstrated on nasal SIgA secretion.