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B. Manickam, P. S. Bora, N. S. Bora; Role of Classical, Alternative and Lectin Pathways in the Induction of Experimental Autoimmune Anterior Uveitis (EAAU). Invest. Ophthalmol. Vis. Sci. 2008;49(13):4750.
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We have previously shown that complement activation plays a critical role in the development of experimental autoimmune anterior uveitis (EAAU). However, the specific pathway involved in the activation of complement during EAAU is not known. The objective of the present study was to determine the levels of C1q (component of the classical pathway), C4 (component of classical and lectin pathways) and factor B (component of the alternative pathway) during EAAU. This would help us to delineate specific pathway(s) involved in the induction of EAAU.
Lewis rats were immunized with melanin associated antigen (MAA) emulsified (1:1) in complete Freund’s adjuvant. Animals were examined daily between days 7 and 30 after injection for clinical signs of uveitis using slit lamp biomicroscopy and EAAU was graded in a masked fashion. Eyes were harvested from MAA-injected rats at various time points for histologic analysis to assess the course and severity of inflammation. The eyes were harvested at day 10, 14, 19, 23 and 30 post-immunization to determine mRNA and protein levels of C1q, C4 and factor B using RT-PCR and Western blot analysis respectively.
RT-PCR and Western blot analysis revealed that both mRNA and protein levels of C1q and C4 did not change during the course of EAAU and were similar to those observed in naïve animals. Interestingly, the expression of factor B mRNA and protein was up-regulated within the eyes at the onset of EAAU and remained elevated during the peak of disease. Factor B levels declined during the resolution of EAAU and returned to basal levels (similar to naïve animals) when the disease resolved.
These results suggest that complement activation via the alternative pathway might be critical for the induction of EAAU. Our future experiments would involve the silencing of C1q, C4 and factor B genes using siRNA to confirm which specific pathway(s) of complement activation is crucial for the induction of EAAU.
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