The role of the spleen and splenectomy in autoimmune hemolytic disease.

The relationship of the spleen to the red cell in AHDW is determined by the characteristics of the surface protein coating of the red cell, rather than by a pathologic change in the reactivity of the spleen. The behavior of the spleen is essentially a passive response to red cells with abnormal properties. The critical properties are incompletely defined, but probably include cell shape, and perhaps more importantly, the intrinsic properties of the cell membrane. The effects produced by the spleen are mediated partly by the filtration mechanism of the splenic sinus walls, and partly by the more specific effects of cell-to-cell adhesion between the pulp macrophages and the red cells. The outcome is more complex than former concepts of red cell destruction encompassed: delay in cell passage produces cell pooling in the unfavorable environment of the splenic pulp, and there is microfragmentation, cell sphering, and partial phagocytosis, in addition to cell destruction with erythrophagocytosis in situ. Prediction of the degree of dependence of hemolysis on the spleen prior to splenectomy remains an area of uncertainty. Commonly, the decision for splenectomy is determined circumstantially, but current concepts would anticipate that the most relevant data would relate to the dimensions of splenic pooling, and the quantity and class of immunoglobulin present on the cells.