Comparative Characterization of Non-professional and Professional Phagocyte Responses to Apoptotic Cells

Abstract

Cells that die by apoptosis are rapidly removed in vivo, both by neighbouring tissue cells (‘non-professional phagocytes’) and by the professional phagocytes of the innate immune system, macrophages and dendritic cells. This ongoing process of death and removal of dying cells appears silent at the level of the organism, with cells melting away and replacement cells taking their place. However recent advances in the study of dying cell removal and particularly studies of the consequences of defective apoptotic cell removal reveal that this process is far from silent at the cellular level and contributes critically to tissue homeostasis and immune regulation. This occurs through the stimulation of distinct responses by cells following engagement of apoptotic cells. The nature of these responses and how they appear tailored for the phagocyte and the context of apoptotic cell removal are reviewed and discussed here.