Abstract
Purpose :
Defining conditions that promote or suppress immune cells recruitment to the CNS is an area of active investigation. To analyze these conditions as they might occur in-vivo we sought an experimental autoimmune retinitis (EAU) model that avoided ex-vivo manipulations such as adjuvants and adoptive transfer of in-vitro activated T cells.
Methods :
We employed the R161H TCR transgenic model (B10.R3 background) of EAU (Horai, et. al. J Autoimmunity 44:21, provided by Dr. R. Caspi) in parabiosis with transgenic mice (C57BL6) that allow tracking and depletion of activated, antigen presenting microglia (CD11c-DTR/GFP mice) or CX3CR1+ myeloid cells, as well as mice having a fluorescent reporter for Tregs (FoxP3-GFP). Parabiotic mice were made using B10.R3 x B6 F1 mice that carried R161H with or without the B6 transgene to similar mice without R161H. Analysis was done by retinal imaging, flow cytometry, and histology.
Results :
The utility of the B10.R3 x B6 F1 background was established in unpaired mice. The influx of myeloid cells and R161H T cells into the retina was limited in time, peaking at 60-80 days of age, but highly variable in cell number per retina. The severity of EAU was also highly variable. In parabiotic pairs, age of the R161H partner at joining, duration of joining, and EAU activity in the R161H donor were important factors in the development of EAU in the partner mouse. Seven of ten pairs joined with the R161H mouse at 64-165 days of age developed EAU while 0/7 pairs using R161H mice older than 175 days developed EAU (p < 0.01). Joining R161H mice with active EAU transferred disease to 6/6 partner mice while R161H mice whose disease was resolved prior to parabiosis failed to transfer disease to its partner (0/5, p < 0.01). Parabiotic mice joined for a duration of 10 to 43 days did not transfer EAU (0/6) but 8/11 pairs joined for 44-147 days did transfer EAU (p < 0.01).
Conclusions :
Although pathogenic T cells are continuously made and present in R161H mice, the disease spontaneously resolves leaving various degrees of structural damage. While Treg numbers were low compared to effector T cells in actively inflamed retinas, Tregs were in greater proportion in convalescent retinas. Using parabiotic mice we establish that both pathogenic R161 T cells and GFP+ macrophages could be recruited to the recipient retina that developed EAU.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.