Abstract Text: Studies of immune privilege mechanisms demonstrate that the ocular microenvironment is anti-inflammatory and the melanocortin pathway has a central role. Based on our findings that soluble factors produced by the retinal pigment epithelial cells (RPE) alter the response of macrophages to pro-inflammatory signals, we assayed for the potential of RPE regulation of innate immune memory. The conditioned media (CM) of RPE eyecups, intact RPE monolayer, choroid, and sclera of the posterior eye segment, from the eyes of C57BL/6 naive mice and mice with active experimental autoimmune uveitis (EAU) were assayed. Resting peritoneal macrophages were treated with the RPE-CM for 24 hours, washed, and rested for 48 hours. The macrophages were then stimulated with LPS for 24 hours, and the cultures were assayed for TNF-a and IL-10 by ELISA. To initially assess a potential role for the melanocortin pathway, macrophages were treated with the neuropeptide α-MSH instead of RPE-CM and assayed for NO• and IL-1 after LPS addition. The macrophages not pre-treated with CM significantly (P < 0.001) produced TNF-a and no IL-10. Pretreatment with naive RPE-CM had lower, but not statistically significant, TNF-a production; however, there was a significant (P < 0.001) elevation in IL-10 production. In comparison, macrophages pretreated with EAU RPE-CM had no significant change in TNF-a but had only background levels of IL-10. The a-MSH pretreatment of macrophages significantly (P < 0.05) suppressed NO• generation but not IL-1. The results suggest that the RPE can potentially mediate innate immune memory selectively.
