The fate of the phagosome: conversion to 'age pigment' and impact in human retinal pigment epithelium.

Phagosomes are converted to phagolysosomes and then to residual bodies (also known as lipofuscin granules or age pigment). Lipofuscin granules of retinal pigment epithelial (RPE) cells of single human eyes were isolated and analysed for enzyme content and fluorescence spectra. The granules are low in lysosomal enzymes and they fluoresce yellow-gold. Thin layer chromatography reveals several separable constituents. Lipofuscin granules accumulate with age, the largest increase occurring after the first decade of life in humans. Macular RPE cells accumulate granules more than non-macular cells.