Complement, innate immunity and ocular disease.
The complement system is a major component of innate immunity. During an inflammatory reaction, the eye is potentially threatened by homologous complement attack, and unregulated complement activation could lead to tissue damage and vision loss. The complement system is continuously activated at low levels in the normal eye, and intraocular complement-regulatory proteins (CRPs) tightly regulate this spontaneous complement activation so that there is elimination of potential pathogens without the induction of destructive intraocular inflammation. The presence of a complement activation product (iC3b) during the early phase of antigen and antigen-presenting cell contact is essential for the induction of systemic tolerance to antigen injected into the anterior chamber of the eye and the establishment of ocular immune privilege. The complement system and complement-regulatory proteins control intraocular inflammation in autoimmune anterior uveitis and may play an important role in the development of age-related macular degeneration. Thus, in the eye, complement functions as a double-edged sword - on one hand it provides innate immunity against pathogens while simultaneously instructing the adaptive immune response to develop tolerance to such pathogens to avoid inadvertent tissue damage in a critical organ.
Sohn
Jeong-Hyeon
JH
Department of Ophthalmology, Jones Eye Institute, University of Arkansas for Medical Sciences, Little Rock, Ark., USA.
Bora
Puran S
PS
Jha
Prushottam
P
Tezel
Tongalp H
TH
Kaplan
Henry J
HJ
Bora
Nalini S
NS
D000818:Animals; D000867:Anterior Chamber / Q000276:immunology; D003167:Complement Activation; D003165:Complement System Proteins / Q000502:physiology*; D005128:Eye Diseases / Q000276:immunology*; D006801:Humans; D007108:Immune Tolerance; D007113:Immunity, Innate; D008268:Macular Degeneration / Q000276:immunology; D014605:Uveitis / Q000276:immunology
D003165:Complement System Proteins