Abstract
The red of the spleens from three patients with autoimmune hemolytic anemia and two with Evans' syndrome was examined by electron microscopy. In the cases in which splenectomy was done as the first choice of therapy, phagocytosis of sensitized red cells by the cordal macrophages was more frequent comparing to the cases which were given corticosteroids before the operation. At the early stage of erythrophagocytosis, intact-appearing red cells were observed within the phagocytic vacuoles of macrophages. As the intracellular digestion progressed, small, electron dense daughther vacuoles appeared around the initial erythrophagocytic vacuoles, which turned to be less dense and usually contained partially destructed red cell membrane.
Partial phagocytosis or surface microfragmentation by the cordal macrophages was suggested as a possible mechanism of immune spherocytosis. However, this finding was rather infrequent and contribution of other mechanisms, such as membrane damage by lysosomal enzymes released from macrophages and metabolic conditioning in the splenic cord, must be considered.
In addition to the unique anatomical structures of the red pulp, agglutination of red cells by antibodies and reduced deformability of immune spherocytes are responsible for the stagnation and hemoconcentration in the splenic red pulp, which ultimately promote immune adherence and phagocytosis of red cells by the macrophage.
