Secretory immune system of rabbit ocular adnexa.

A distinct system of immunity in a variety of animals is located subjacent to epithelial surfaces and is typified by the predominance of immunoglobulin A (IgA) and secretory component (SC) in various external secretions, including tears. The present study examined normal rabbit lacrimal gland, conjunctiva, and cornea for the presence of immunoglobulin and SC. IgA-staining plasma cells predominated within lacrimal gland and conjunctival stroma, and SC was found in the epithelial cells of both these tissues but not within corneal epithelium. These observations are consistent with findings for other secretory sites in both rabbits and humans and establish lacrimal gland and conjunctiva as integral parts of the rabbit secretory immune system.