HUMAN CORNEAL EXTRACT ENHANCES SERUM COMPLEMENT ACTIVITY

Purpose. The concomitant presence of complement-activation products in the cornea during inflammation is well described. The present study w as undertaken to analyze the complement activity of normal human corne al tissue and to assess the presence of complement-modulating activiti es. Methods. Human corneal tissue was extracted in veronal-buffered sa line. The overall complement (C) activity of the human corneal extract (HCE) and the effect of HCE on serum C-activity were investigated usi ng a hemolytic assay. Anion-exchange chromatography and gel filtration were applied for biochemical analysis of HCE. Monoclonal anti-human C 3 was used to detect corneal C3 and to remove C3 from HCE by immunoads orption. Results. It was found that C-activity of HCE was less than 20 0 U/g tissue. Experiments to test whether HCE exhibited inhibitory act ivity led to an unexpected result: When added to human serum dilutions , HCE caused a significant, dose-dependent increase of C-activity. Pre treatment of HCE at 56 degrees C abolished the effect. Analysis of HCE by anion-exchange chromatography revealed two C-enhancing peaks. One peak was identified as C3 whereas the identity of the other protein pe ak remained unknown. Conclusions. Results indicate that the human corn ea contains an as yet unidentified heat sensitive factor(s) able to en hance complement activity of serum. It is postulated that this factor( s) may play an important role in corneal physiology and pathology.