Purpose: We performed an immunohistochemical study on the development of interstitial keratitis in a rabbit model sensitized by ovalbumin (OA).
Methods: A mixture of OA (5 micrograms/ml) and Freund's complete adjuvant was initially injected subcutaneously (0.4 ml) into the rabbits' back and footpad (0.2 ml). After a week, the rabbits were sensitized by an injection of the same solution into the back (0.5 ml) again. After 4 weeks the rabbits underwent the same treatment as a booster shot. Then a week later OA solution (0.05 ml) was injected into the corneal stroma. We observed the cornea on days 1-3, 7, and 10 after the corneal treatment. Corneas on days 3 and 10 were examined by immunohistological methods using hematoxylin-eosin stain, methylgreen pyronin stain, and by immunohistochemical methods with anti-CD 4, anti-CD 8, and anti-OA antibodies. The localization of specific antibodies was identified by fluorescent-antigen method. Electron-microscopic observation was also done.
Results: Rabbits developed corneal opacity and edema on day 1, corneas had on immune ring with a peak intensity on day 3, and vascularization on day 7 after corneal treatment. Microscopic examination revealed infiltration of neutrophils in to the area of the immune ring on day 3 and many plasma cells at the limbus and stroma on day 10. CD 4 positive cells were found at the limbus and stroma on days 3 and 10. CD 8 positive cells were found at the limbus and stroma only on day 10. OA positive findings were observed at the immune ring and its inner area. In the fluorescent-antigen method, specific antibodies were found in plasma cells at the limbus on days 3 and 10.
Conclusions: In our experimental model of interstitial keratitis with immune ring and vascularization, the Arthus reaction was dominant. Infiltration of antigen specific plasma cells in the stroma with vascularization caused a modification of pathologic reaction in keratitis.