Qa-1, a Nonclassical MHC Molecule with Immunomodulatory Functions, Is Ubiquitously Expressed in the Immune-Privileged Anterior Chamber of the Eye

Abstract

Purpose: To determine whether the MHC class Ib gene, Qa-1, is expressed in the tissues that surround the immune-privileged anterior chamber (AC) of the murine eye. Methods: Transcription of Qa-1 mRNA in BALB/c ocular tissues was analyzed by reverse transcription-polymerase chain reaction. Expression of Qa-1 protein was assessed on ocular frozen tissue sections by immunohistochemistry, and within aqueous humor by western blotting. Results: Transcription of Qa-1 was found in all tissues surrounding the AC of the eye. Immunohistological staining revealed Qa-1 expression on corneal endothelium, corneal epithelium, and lens epithelium. No soluble Qa-1 was detected in aqueous humor. Conclusions: Qa-1, unlike other MHC class I molecules, is ubiquitously expressed in tissues surrounding the AC of the eye, raising the possibility that Qa-1 plays a role in creating and maintaining ocular immune privilege.