The morphology of echinoid phagocytes and mouse peritoneal macrophages during phagocytosis in vitro

The morphology of mouse peritoneal macrophages and echinoid phagocytes during phagocytosis in vitro was studied. A striking similarity in the function of the foreign surface receptor is found in the two systems. Glutaraldehyde-treated erythrocytes attached randomly over the entire surface of the cells and were internalized without circumferential attachment between the particles and the phagocyte membrane. The particles seemed to sink directly into the cytoplasm of the cells. Tannin-treated erythrocytes were phagocytosed by the echinoid cells in a similar mode. The complement-coated erythrocytes were attached only in the perinuclear area of the echinoid phagocyte's membrane, but the morphology of their internalization was similar to that mediated by the foreign surface receptor. A circumferential attachment between the particles and the phagocyte membrane did not seem necessary. This is also the case for mouse peritoneal macrophages.