Eighteen patients with acquired hemolytic anemia were studied with particular reference to the direct and indirect antiglobulin (Coombs) reaction. The abnormal antibodies present were of the warm type in eleven patients and of the cold type in seven patients.
With warm antibodies a well marked zone of inhibition was usually observed when sensitized red cells were suspended in high concentrations of antiglobulin serum, and the reaction was readily inhibited by the previous addition of very small amounts of human γ globulin to the antiglobulin serum. Acidification of the serum to pH 6.5 caused in most cases a moderate increase in the intensity of sensitization in the indirect antiglobulin test. Previous heating of the serum at 56 C. for 30 minutes did not prevent sensitization.
With cold antibodies, on the other hand, no inhibition of the antiglobulin reaction took place in the highest concentration of antiglobulin serum used, and the reaction was not inhibited by the previous addition of small amounts of human γ globulin to the antiglobulin serum. Acidification of the serum to pH 6.5 caused, in most cases, a considerable increase in the intensity of the reaction. Previous heating of the serum at 56 C. for 30 minutes completely prevented sensitization.
The separation of the abnormal antibodies of acquired hemolytic anemia into warm and cold types cuts across clinical classification. Warm antibodies were found in the majority of idiopathic cases; cold antibodies were present in some idiopathic cases and in hemolytic anemia following virus pneumonia. Splenectomy was followed by sustained remissions in some of the idiopathic cases of both the warm antibody and cold antibody varieties.