Quantifying FITC-labeled latex beads opsonized with photoreceptor outer segment fragments: an easy and inexpensive method of investigating phagocytosis in retinal pigment epithelium cells.

The retinal pigment epithelium (RPE) is the most active phagocyte in the human body, and this function is indispensable for vision. In this study, we introduce an easy and inexpensive way to quantify RPE phagocytosis by opsonizing FITC-labeled latex beads of a defined size with a crude mixture of photoreceptor outer segment fragments, using cells of porcine origin. After performance of the desired experiment, phagocytosis can easily be quantified by counting the ingested particles. With this protocol, we combine the advantage of a natural target with the advantages of the defined properties of latex beads. Moreover, in order to conduct these phagocytosis experiments, as laboratory equipment, in addition to cell culture equipment, only a centrifuge and a simple fluorescence microscope are needed.