The author tried to determine the secretory immunoglobulin A (SIgA) level in the whole saliva of healthy subjects and patients with oral diseases by the enzyme-linked immunosorbent assay (ELISA) technique. An ELISA system that was previously developed for determining the SIgA level in the pancreatic juice was modified and was proved to be applicable for the SIgA in the whole saliva. It was found that the SIgA in the whole saliva could be determined with excellent reproducibility and linearity when the samples were diluted 1,000-fold. This assay method was superior to the conventional techniques in terms of accuracy, covering a wide range SIgA levels in the saliva.
In the 74 healthy subjects, the SIgA level in the whole saliva did not show any major age- or sex-related difference. However, patients with leukoplakia, lichen planus and carcinoma in the oral cavity showed higher levels of SIgA. The elevated levels of SIgA in the saliva of these patients suggested that some local changes in immunological competence might occur due to prolonged exposure to the antigen in the oral cavity.