Secretory Component and IgA in the Endolymphatic Sac

Abstract

Immunohistochemical methods were used to investigate secretory component (SC) and immunoglobulin A within the inner ears of Sprague Dawley rats and BALB/c mice. Utilizing specific antisera against SC and IgA, the distribution and localization of SC and IgA were studied in normal, non-immunized ears of both animal species. The kinetics of SC and IgA were also investigated during a secondary immune response following keyhole limpet hemocyanin (KLH) challenge of murine inner ears. In the non-immunized murine inner ear, neither SC or IgA were found. In contrast, SC was localized within the epithelial cells and lumen of the endolymphatic sac (ES) in non-immunized rats and faint luminal IgA staining was seen in one-third of the animals, as well as an occasional IgA-bearing cell in the ES. In the inner ear secondary immune response, SC was found only within the endolymphatic sac of approximately 50% of the immunized mice 14 days after KLH challenge. IgA-bearing cells were also observed within the ES 2 to 3 weeks following KLH challenge. We conclude that there are species differences in the distribution of SC and IgA within the inner ear, and that under pathological conditions the endolymphatic sac may be a site of IgA and SC induction.

Key Words:

• secretory component
• IgA
• inner ear
• mucosal immunity