Immunology of the ocular surface.

The ocular surface immunity is a remarkable combination of the innate immune and adaptive immune systems, designed to prevent microbial invasion while minimizing damage to delicate ocular tissue. The innate immune system uses a variety of methods to minimize microorganism invasion, including mechanical tissue barriers and production of antimicrobial peptides. Tolerance of normal ocular flora is achieved by the presence of a minimal number of professional antigen presenting cells, immunosuppressive substances in tears, and the strategic intra- and intercellular location of the Toll-like receptors. Autoimmune diseases are common on the ocular surface, and with contributions of environmental and genetic factors, autoantigens are presented to the adaptive immune response. Toll-like receptors are the link between the innate and adaptive immune response, and are likely key components of the response of ocular tissue to infectious organisms and in the initiation and perpetuation of autoimmune disease.