Dog red cells heated at 49 C. for 15 minutes with no change in osmotic fragility, showed a decreased rate of survival in vivo, and increased sequestration by the spleen, and an increase in the osmotic fragility when recovered from the spleen. The peripheral blood showed normal osmotic fragility at all times. These changes were comparable to those seen in the spleen in homozygous sickle-cell disease and hereditary spherocytosis. There was no hemoglobinemia. Splenectomy decreased the rate of destruction of such heated red cells in vivo. In these studies the rigidity of the red cells with increased viscosity, but with normal osmotic fragility, may have resulted in the removal of the heated red cells by the spleen and subsequent conditioning of these cells in the spleen.
In contrast to the 15 minutes heating, dog cells heated at 49 C. for 60 minutes had increased osmotic fragility and were rapidly removed from the circulation. There was sequestration by the spleen or by the liver with hemoglobinemia. The red cells with the greatest increase in osmotic fragility were not preferentially removed in vivo.