Local and Systemic Complement Activation in Experimental Autoimmune Anterior Uveitis

Abstract

Abstract: : Purpose: To study the local and systemic complement acivation and its role in experimental autoimmune anterior uveitis (EAAU). Methods: EAAU was induced in Lewis rats by immunization with bovine melanin associated antigen (MAA) emulsified in Freund’s complete adjuvant and pertusis toxin. The rats were sacrificed (n=6/time point) at day 8, 10, 12, 14, 16, 19, 23 and 30 post–immunization. Serum complement levels were monitored using CH50 hemolytic assay and complement levels in eye were monitored by semi–quantitative Western blot for C3 split products. In some experiments Lewis rats were injected with bovine serum albumin (BSA) emulsified in Freund’s complete adjuvant and pertusis toxin. Some animals received a single injection of cobra venom factor (CVF, >30 units/rat, i.p.) to deplete complement. Results: The increase in serum complement activity followed the same trend as the disease activity and we found a strong correlation between the serum complement activity and the clinical score of EAAU. The serum complement activity remained elevated in BSA injected animals at all time points. In the animals injected with MAA the C3 level in the eye, as detected by Western blot, were high during the peak of the disease and the levels returned to basal levels as the disease resolved. No change in C3 levels was observed in the eyes of BSA injected animals and the level remained at baseline level. These animals did not show any sign of ocular inflammation. A single injection of CVF on day 9 post–immunization resulted in complete depletion of complement for 5 days in MAA injected animals. The complement activity returned to the basal levels (similar to naïve) on day 16 and remained at this level from day 19–30. C3 split products were not detected within the eye of CVF treated MAA injected Lewis rats. Conclusions: Our results provide strong evidence that complement activation contributes to the development of EAAU.

Keywords: autoimmune disease • inflammation • uveitis-clinical/animal model