Autoimmune haemolytic anaemias. IV. Biochemical studies of red cells from patients with autoimmune haemolytic anaemia with incomplete warm autoantibodies.

The most noticeable biochemical abnormality of red cells of patients with autoimmune haemolytic anaemia with warm autoantibodies is the increased osmotic fragility of the red cells. This appeared to be most pronounced in patients with incomplete IgG warm autoantibodies and to be significantly correlated with the 51Cr T½ of the patients' red cells. It appeared to be a disturbance of the cells which slowly increased with time. It only occurs in vivo and the reaction of the cell with the autoantibodies is necessary. Possibly, it is caused by damage done to the sensitized red cells by the RES. It is accompanied by an increased K+ efflux of the red cells. Interaction of red cells and antibody in vitro has no effect. A number of other biochemical abnormalities, such as increased enzyme activities, increased glycolysis and ATP breakdown, also correlated with the 51Cr T½ are probably the result of the lower mean cell age of the red cells.