Generation of complement membrane attack complex in normal human corneas

To determine whether complement-derived SC5b-9, the soluble nonlytic-fluid phase of the membrane attack complex, can be generated in normal human corneas when they are injured with lipopolysaccharide (LPS), ribitol teichoic acid (RTA) immune complexes, acid, or alkali.

The experimental cornea of each donor pair was injected with 50 microliters of sterile saline containing 0.5 mg of LPS or 50 microliters of sterile saline containing 250 micrograms of RTA immune complexes. Other experimental corneas were treated topically for 35 seconds with either 200 microliters of 1N HCl or 2N NaOH. The control cornea of each donor pair was injected with 50 microliters of sterile saline or was treated topically for 35 seconds with 200 microliters of sterile saline. After injury, all corneas were incubated in medium 199 for 6 hours at 37 degrees C in 5% CO2, then eluted for 24 hours in phosphate-buffered saline with 10 mM ethylenediaminetetraacetic acid. Each corneal eluate was collected and stored at -70 degrees C until assayed for SC5b-9 by an enzyme immunoassay.

Compared with control corneas, SC5b-9 levels were increased significantly in corneas injected with LPS or RTA immune complexes. However, when compared with controls, SC5b-9 levels were decreased significantly in corneas treated with HCl or NaOH.

Normal human corneas injured immunologically with LPS or RTA immune complexes activate the classical or alternate pathway and generate SC5b-9. Corneas injured chemically with acid or alkali do not produce SC5b-9.