Erythrophagocytosis by the sinus endothelial cell of the spleen in haemolytic anaemias.

An ultrastructural study of spleens from patients with a heterogeneous group of haemolytic anaemias was undertaken in order to determine whether sinus endothelial cells have erythrophagocytic ability. In most cases, sinus endothelial cells contained erythrocytes and various stages of intracellular degradation of engulfed erythrocytes were noted. Though the frequency of erythrophagocytosis varied from case to case, phagocytosis of erythrocytes by the endothelial cell was more frequent in cases in which cordal macrophages showed active erythrophagocytosis. These results suggest that the sinus endothelial cells have erythropagocytic ability in certain pathological states, especially when the demands for the removal of defective erythrocytes are increased. However, the bulk of erythrophagocytosis is carried out by cordal macrophages, and endothelial phagocytosis has a minor significance in the developemnt of haemolytic anaemia. Two possible processes by which erythrocytes come into contact with sinus endothelial cells are suggested.