Abstract
Purpose: :
To investigate the role of decay accelerating factor (DAF), a cell surface complement regulator that recently has been linked to T cell responses and autoimmunity in the pathogenesis of experimental autoimmune uveitis (EAU).
Methods: :
We evaluated retinal injury, IRBP specific T cell responses and cytokine expression profiles in mice deficient in Daf1, the mouse homologue of human DAF and in WT mice treated with recombinant soluble mouse DAF protein. To compare disease severity in WT and Daf1-/- mice, we induced EAU in 16 mice of each group by immunizing each mouse with 100 µg of IRBP1-20 emulsified in CFA supplemented with 2.5 mg/ml M tuberculosis strain H37RA extract s.c. together with 1.5 µg pertussis toxin i.p. Twenty one days later, we enucleated eyes for histopathological assessments and collected splenocytes for Th1/Th17 response assays and cytokine antibody array assays. To compare disease severity and T cell responses in WT mice with and without soluble DAF protein treatment, we induced EAU in 10 disease susceptible B10.RIII mice by immunizing 5 µg of IRBP161-180 in CFA s.c. and treated 5 mice with 0.5 mg soluble DAF protein i.p. every other day and other 5 with equal volume of PBS. We compared retinal histology and IRBP specific T cell responses in 14 days as done above.
Results: :
We found that both EAU incidence (Daf1-/- 87.5% vs WT 50%) and histopathology scores (Daf1-/- 1.86±1.08 vs WT 0.73±0.56) were significantly greater in Daf1-/- mice. There were >10 fold greater mononuclear cell influx into the retina together with severe vasculitic lesions, retinal folding and photoreceptor cell layer destruction. IFN- and IL-17 ELISPOT assays showed that spleens from Daf1-/- mice contained 5-7 fold more IFN-γ producing and 3-4 fold more IL-17 producing T cells than spleens from WTs. Cytokine array assays showed that splenocytes from Daf1-/- mice with EAU express elevated levels of GM-CSF, IL-2, IL-3 and IFN-γ. Consistent with these results, WT B10.RIII mice that received soluble DAF protein treatments exhibited decreased IRBP specific Th1/Th17 responses and were protected from retinal injury compared to mice received PBS treatments.
Conclusions: :
DAF significantly influences IRBP specific Th1 and Th17 responses and disease severity in EAU. Systemic upregulation of DAF levels could be used to suppress retinal antigen(s) specific autoimmunity to treat autoimmune posterior uveitis.
Keywords: uveitis-clinical/animal model • immunomodulation/immunoregulation • transgenics/knock-outs