Abstract
Purpose: :
Objective of the current study was to delineate the pathway of complement activation that is crucial for the induction of experimental autoimmune anterior uveitis (EAAU).
Methods: :
EAAU was induced in Lewis rats by immunization with melanin associated antigen (MAA). We studied the development of EAAU in animals treated with antibody against C4 and factor B. MAA sensitized Lewis rats received eight injections (0.5 mg/kg) at 24 h interval of C4 or factor B antibodies via the intraperitoneal (ip) route at days 4, 5, 6, 7, 8, 9, 10 and 11 post-immunization. Control animals received a similar treatment with isotype IgG control. For adoptive transfer EAAU, T cells obtained from the popliteal lymph nodes of anti-factor B or isotype control antibody treated Lewis rats, were injected intravenously via the tail vein into naïve syngenic animals. Levels of TNF-alpha and IFN-gamma were measured using ELISA. The T cell proliferation was investigated using flow cytometric analysis of CFSE stained CD4+ T cells.
Results: :
Antibody against C4 had no effect on EAAU and all animals developed EAAU similar to those injected with control IgG. In contrast, EAAU was completely inhibited in all MAA sensitized Lewis rats injected ip with factor B antibody. Treatment with anti-factor B antibody resulted in suppression of ocular complement activation. Adoptive transfer of lymphocytes harvested from draining lymph nodes of donor animals treated with anti-factor B did not transfer EAAU to naïve syngenic rats. Anti-factor B antibody inhibited the ability of MAA specific CD4+ T cell to proliferate (in vitro) in response to MAA in a dose dependent manner. Level of TNF-alpha and IFN-gamma decreased in the presence of anti-factor B.
Conclusions: :
Collectively, our results provide the novel finding that complement activation via the alternative pathway contributes to intraocular inflammation in EAAU and anti-factor B mediated inhibition of EAAU is due to diminished antigen specific CD4+ T cell responses to MAA.
Keywords: inflammation • uveitis-clinical/animal model • autoimmune disease