Chronic low level complement activation within the eye is controlled by intraocular complement regulatory proteins.
OBJECTIVE
To explore the role of the complement system and complement regulatory proteins in an immune-privileged organ, the eye.


METHODS
Eyes of normal Lewis rats were analyzed for the expression of complement regulatory proteins, membrane cofactor protein (MCP), decay-acceleration factor (DAF), membrane inhibitor of reactive lysis (MIRL, CD59), and cell surface regulator of complement (Crry), using immunohistochemistry, Western blot analysis, and reverse transcription-polymerase chain reaction (RT-PCR). Zymosan, a known activator of the alternative pathway of complement system was injected into the anterior chamber of the eye of Lewis rats. Animals were also injected intracamerally with 5 microl (25 microg) of neutralizing monoclonal antibody (mAb) against rat Crry (5I2) or CD59 (6D1) in an attempt to develop antibody induced anterior uveitis; control animals received 5 microl of sterile phosphate-buffered saline (PBS), OX-18 (25 microg), G-16-510E3 (25 microg), or MOPC-21 (25 microg). The role of complement system in antibody-induced uveitis was explored by intraperitoneal injection of 35 U cobra venom factor (CVF), 24 hours before antibody injection. Immunohistochemical staining and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with Western blot analysis were used to detect the presence of membrane attack complex (MAC) and C3 activation products, respectively, in normal and antibody-injected rat eyes.


RESULTS
Complement activation product MAC was present in the normal rat eye, and intraocular injection of zymosan induced severe anterior uveitis. The complement regulatory proteins, MCP, DAF, CD59, and Crry, were identified in the normal rat eye. Soluble forms of Crry and CD59 were also detected in normal rat aqueous humor. Severe anterior uveitis developed in Lewis rats injected with a neutralizing mAb against Crry, with increased formation of C3 split products. Systemic complement depletion by CVF prevented the induction of anterior uveitis by anti-Crry mAb. Intracameral injection of anti-rat CD59 (6D1), anti-rat MHC class I antigen (OX-18), anti-rat Ig (G-16-510E3), or MOPC-21 caused no inflammatory reaction.


CONCLUSIONS
The results suggest that the complement system is continuously active at a low level in the normal eye and is tightly regulated by intraocular complement regulatory proteins.
Sohn
J H
JH
Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO, USA.
Kaplan
H J
HJ
Suk
H J
HJ
Bora
P S
PS
Bora
N S
NS
D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis* / Q000235:genetics; D000954:Antigens, Surface; D001483:Base Sequence; D015153:Blotting, Western; D018958:CD55 Antigens / Q000096:biosynthesis* / Q000235:genetics; D018957:CD59 Antigens / Q000096:biosynthesis* / Q000235:genetics; D003167:Complement Activation; D015941:Complement Hemolytic Activity Assay; D003170:Complement Pathway, Alternative / Q000502:physiology*; D017931:DNA Primers / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D005123:Eye / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D008297:Male; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011917:Rats, Inbred Lew; D011956:Receptors, Cell Surface; D011951:Receptors, Complement / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013047:Specific Pathogen-Free Organisms; D014606:Uveitis, Anterior / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D015054:Zymosan / Q000008:administration & dosage
D015703:Antigens, CD; D000954:Antigens, Surface; D018958:CD55 Antigens; D018957:CD59 Antigens; C497860:Cd46 protein, rat; C513105:Cr1l protein, rat; D017931:DNA Primers; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011951:Receptors, Complement; D015054:Zymosan