Elimination of old or worn red blood cells in the senile murine spleen.

After amyloid had deposited in the perifollicular area, cells contained iron disappeared in the red pulp but remained in the lymphoid follicles. Red blood cells must pass a slit of amyloid in the perifollicular area. Red blood cells become mechanically more fragile as they age. Hemoglobin in the serum is not engulfed by splenic macrophages. Disappearance of cells contained iron in the red pulp indicated that old or worn red blood cells are eliminated more by mechanical stress than by phagocytosis of macrophage in the senile spleen having amyloid deposition.