[Validity limits of data on secretory IgA].
Secretory IgA (sIgA) in saliva, and sometimes in expectoration, have been titrated in various groups of persons, both in pediatric age and in adults, by means of radial immunodiffusion technic. The aim was to find differences among sIgA levels in the course of respiratory tract infections, both acute and chronic, in consequence of treatment with Erythromycin (in children and in adults) in consequence of surgical intervention (in adults). Adjunctive aim was to establish if it was possible to recognize hereditary of the character that remark the predisposition to produce high sIgA quantities. The very high variability of the data collected in the various occasions and situations allowed serious doubts about the possibility of use of the parameter sIgA in saliva for the evaluations that were assumed as aim of the research. The said high variability was confirmed in a single surely healthy boy, in which sIgA were performed on saliva specimens collected for ten consecutive days, morning and evening, always at the same time (8 a.m. and p.m.). In the attempt to clarify the reason of such a variability, the intervention of psychical solicitation and emotional conditions were ipotized to modify production, mobilization and secretion of IgA generally considered and sIgA particularly.