Conjunctival instillation of retinal antigens induces tolerance Does it invoke mucosal tolerance mediated via conjunctiva associated lymphoid tissues (CALT)?

Abstract

Conjunctiva associated lymphoid tissue (CALT) is histologically very similar to other mucosa associated lymphoid tissue (MALT) like gut associated lymphoid tissue (GALT) and bronchus associated lymphoid tissue (BALT), and forms an integral part of the mucosal immune system. Several studies have shown that antigens encountered by GALT and BALT, induce a state of tolerance rather than sensitization. This MALT induced suppression of immune responses against antigen is manifest in both the humoral and cell mediated components of the immune system. The phenomenon of mucosa induced tolerance to a variety of antigens, including retinal antigens, has been well documented with regard to GALT and BALT. However, similar information concerning CALT is not available. In this preliminary study, using retinal antigens and the experimental autoimmune uveitis (EAU) model, we were able to demonstrate that antigen specific tolerance to two retinal antigens, S-antigen and interphotoreceptor retinol-binding protein (IRBP), could be effectively induced by instillation of the antigens into the conjunctival sac for ten days prior to challenge with the respective antigen. It is likely that tolerance induction by this mode involves CALT.

Key Words:

• Conjunctiva associated lymphoid tissue
• immunological tolerance
• retinal antigen
• experimental autoimmune uveitis