Comparison of the Kinetics of Maturation of Phagosomes Containing Apoptotic Cells and IgG-Opsonized Particles

Defective clearance of apoptotic cells has emerged as an important contributing factor to the pathogenesis of many diseases. Although many efforts have been made to understand the machinery involved in the recognition between phagocytes and potential targets, little is known about the intracellular transport of phagosomes containing apoptotic cells within mammalian cells. We have, therefore, performed a detailed study on the maturation of phagosomes containing apoptotic cells in a non-professional phagocytic cell line. This process was compared with the maturation of IgG-opsonized particles, which are internalized via the Fcγ-receptor (Fcγ-R), one of the best characterized phagocytic receptor, in the same cell line stably expressing the Fcγ-RIIA. By comparing markers from different stages of phagosome maturation, we have found that phagosomes carrying apoptotic particles reach the lysosomes with a delay compared to those containing IgG-opsonized particles. Enrichment of the apoptotic particles in phosphatidylserine (PS) neither changed the kinetics of their engulfment nor the maturation process of the phagosome.