Abstract
Purpose :
We previously reported that retinal pigment epithelial cells (RPE) through melanocortin pathways suppress phagosome maturation within antigen presenting cells (APC). This suppression would significantly affect APC activation of CD4+ T cells. Therefore, we assayed for suppression of APC antigen-activation of CD4+ T cells by RPE from mice with experimental autoimmune uveitis (EAU) and treated with alpha-melanocortin stimulating hormone (α-MSH).
Methods :
Experimental autoimmune uveitis (EAU) was induced in C57BL/6 mice immunized with IRBP peptide in adjuvant, and the mice were treated with α-MSH when EAU reached the chronic phase. At clearance of uveitis, RPE-eyecups were made by making a circumferential cut just under the ciliary body, and discarding the anterior chamber, lens, and neuroretina leaving the RPE monolayer, choroid, and sclera. The RPE-eyecups were incubated in serum-free media for 24 hrs. The conditioned media was removed and used to treat the naive peritoneal macrophages with opsonized ovalbumin for 24 hours. Opsonized rat serum albumin was used as irrelevant antigen control. The APC were washed, and CD4+ T cells isolated from draining lymph-nodes of mice immunized to OVA were added. After 48 hrs incubation, the culture supernatant was assayed by ELISA for IFN-γ, IL-17, and IL-10, and the T cells assayed by flow cytometry for Treg cell markers CD25 and FoxP3.
Results :
APC treated with the conditioned media of RPE-eyecups from naive and α-MSH-treated EAU mice, but not from untreated-EAU mice significantly suppressed IL-17, while significantly enhancing IL-10 production by CD4+ T cells with all RPE-eyecup conditioned media suppressing APC-stimulation of IFN-γ production. While APC treated with the conditioned media of RPE-eyecups from EAU mice significantly enhanced by 2.5-fold the number of CD25+FoxP3- T cells, it was 80% suppressed by RPE-eyecup conditioned media from α-MSH-treated EAU mice that were neither statistically different from the effects of EAU or naive RPE-eyecup conditioned media on APC. None of the RPE-eyecup conditioned media induced APC to expand the population of CD25+ FoxP3+ Treg cells.
Conclusions :
The results demonstrated that APC are influenced by RPE soluble molecules and demonstrated that RPE promote APC maintenance of Treg cells while suppressing expansion of effector T cells. Treatment of EAU with α-MSH supports recovery of RPE regulation of immune cell activity.
This is a 2021 ARVO Annual Meeting abstract.