Secretory immune response in patients with oropharyngeal carcinoma

The secretory immune system is a unique, local immunological mechanism which appears to be independent of systemic immunity. Secretory immunoglobulin A (SIgA), a major component in this mucosal immune system, is structurally different from the IgA immunoglobulin in serum and has a function as a first line of defense against the uptake of macromolecules and against infectious agents in the intestine, respiratory tract and genitourinary system. However, its relationship to the development and control of neoplasia is not well understood despite the fact that the major portion of human malignancies are of the epithelial type and located where the secretory immune system is vigorously functioning. In this study, the amounts of SIgA and secretory component (SC) in oral secretions and sera were measured in 20 patients with oropharyngeal carcinoma and 22 appropriate control subjects in order to elucidate the involvement of the secretory immune system as it related to oropharyngeal carcinoma. Cancer patients had increased IgA levels in oral secretions (561 +/- 161 micrograms/ml) compared to normal subjects (166 +/- 18 micrograms/ml, p less than 0.02) and to a smoker/drinker subgroup of controls (229 +/- 8.7 micrograms/ml, p less than 0.05). The elevated IgA levels in cancer patients appear to be unrelated to local inflammation or the patient's history of smoking or drinking. Density gradient analysis demonstrated that the IgA measured in oral secretions migrates at the 11S position, confirming that it is of the secretory type and indicating that the increased levels of IgA in oral secretions of patients with oropharyngeal carcinoma are not due to nonspecific leakage of 7 SIgA from sera. Secretory component levels in sera also revealed highly significant differences between cancer patients (1.65 +/- 0.73 micrograms/ml) and all control subjects (0.85 +/- 0.12 micrograms/ml, p less than 0.002). The data suggest that the increased SIgA concentration in secretions and SC level in sera accompany the existence of oropharyngeal carcinoma. The biological significance of these findings and their possible clinical application are discussed.