Interleukin-4 Plasma Levels Stratified by Sex in Intermediate Age-Related Macular Degeneration and Geographic Atrophy

Purpose: Chronic local inflammation underlies the pathogenesis of age-related macular degeneration (AMD) causing damage to the neurosensory retina. However, there is minimal research on systemic cell-mediated inflammation in AMD. Interleukin-4 (IL-4) is an immunoregulatory cytokine with an important role in modulating inflammation in chronic immune mediated disease. The purpose of this study was to: (1) investigate the role of systemic IL-4 in patients with intermediate AMD (iAMD) and in geographic atrophy (GA), an advanced form of AMD, compared to controls without AMD, and (2) determine if IL-4 levels are moderated by sex.Methods: We examined plasma levels of IL-4 in patients with iAMD, GA, and controls without AMD included in the University of Colorado AMD registry (August 2014 to June 2021). Cases and controls were defined by multimodal imaging. IL-4 was measured by multiplex immunoassay. Data were analyzed using a nonparametric rank based linear regression model fit to IL-4.Results: There were 199 patients with iAMD, 97 patients with GA, and 139 controls, with a percentage of female patients 61%, 55%, and 66%, respectively. We demonstrated significantly higher median IL-4 levels in GA (35.3; interquartile range [IQR] = 22.8-50.5) compared to iAMD (6.1; IQR = 2.2-11.3, P < 0.01) and controls (10.7; IQR = 5.0-16.8, P < 0.01). There were no significant differences in levels of IL-4 for cases and controls when stratified by sex.Conclusions: These findings demonstrate a systemic immunological difference between iAMD and GA, indicating IL-4 may be a systemic biomarker for GA development.