This dual role of IL-1β is suggested by the in vitro observations that high glucose induces IL-1β in retinal vascular endothelial cells and IL-1β induces its own synthesis in retinal vascular endothelial cells, Müller cells, and astrocytes, combined with the in vivo observation that IL-1β upregulation in the diabetic retina increases progressively in relation to the duration of diabetes. This evidence concerns the gene IL1B and diabetes mellitus.