Origin of crystalloid inclusions in macrophages I: studies of peritoneal macrophages after erythrocyte ingestion.

In an attempt to investigate the origin of crystalloid inclusions present in bone-marrow macrophages of normal adult mice and in man, murine peritoneal macrophages (which normally do not contain inclusions of this nature) were studied by light and electron microscopy 24 h after 3 daily injections of various preparations of erythrocytes. The preparations included mouse erythrocytes with and without pretreatment with collagenase, human erythrocytes and human-erythrocyte ghosts. Crystalloid inclusions were only rarely seen in the peritoneal macrophages in these circumstances. The results offered little support for the idea that crystalloid inclusions are derived from the breakdown of erythrocytes.