Increased Th1/Th17 Responses Contribute to Low-Grade Inflammation in Age-Related Macular Degeneration

Abstract

Background/Aims: Age-related macular degeneration (AMD) is the primary cause of senior blindness in developed countries. Mechanisms underlying initiation and development of AMD remained known. Methods: We examined the CD4 + T cell compartments and their functions in AMD patients. Results: AMD patients presented significantly higher frequencies of interferon (IFN)-γ-expressing and interleukin (IL)-17-expressing CD4 + T cells than healthy controls. The levels of IFN-γ and IL-17 expression by CD4 + T cells were significantly higher in AMD patients. These IFN-γ-expressing Th1 cells and IL-17-expressing Th17 cells could be selectively enriched by surface CCR3 + and CCR4 + CCR6 + expression, respectively. Th1 and Th17 cells from AMD patients promoted the differentiation of monocytes toward M1 macrophages, which were previously associated with retinal damage. Th1 and Th17 cells also increased the level of MHC class I expression in human retinal pigment epithelial (RPE)-1 cells, while Th1 cells increased the frequency of MHC class II-expressing RPE-1 cells. These proinflammatory effects were partly, but not entirely, induced by the secretion of IFN-γ and IL-17. Conclusions: This study demonstrated an enrichment of Th1 cells and Th17 cells in AMD patients. These Th1 and Th17 cells possessed proinflammatory roles in an IFN-γ- and IL-17-dependent fashion, and could potentially serve as therapeutic targets.