Specific and nonspecific humoral defense factors in the epithelium of normal and inflamed gastric mucosa. Immunohistochemical localization of immunoglobulins, secretory component, lysozyme, and lactoferrin.

Epithelial distributions of immunoglobulin A, secretory component, lysozyme, and lactoferrin were studied by paired immunofluorescence staining in ethanol-fixed biopsy specimens from gastric antral and body mucosa. Fluorescence scores were assigned semiquantitatively for the epithelium in three mucosal zones (foveolar, isthmus, and glandular). In each case, degree of inflammation was graded blindly after conventional histologic staining of serial sections. The results showed that the overall epithelial expression of local defense factors was significantly enhanced in association with gastritis, both with regard to nonspecific antimicrobial substances (lysozyme and lactoferrin) and the external transfer of immunoglobulin A (mediated by secretory component) as a potential carrier of protective antibodies. The antral isthmus and glandular zones were most active in both respects. Despite the expression of relatively large amounts of epithelial immunoglobulin A and secretory component in metaplastic glands, these elements lacked the nonspecific defense factors (except for lysozyme in Paneth cells)--even when they occurred in the antral mucosa--and may, therefore, represent particularly vulnerable areas.