An attempt to eliminate platelet antibodies from antilymphocyte serum (ALS) by absorption with unwashed human erythrocytes.

After repeated, 10-20 absorptions of ALS with one-half of its volume of unwashed human erythrocytes, performed each time for 30 min. at room temperature, the titres of the undesired thrombo-agglutinins and thrombolysins can be reduced or these antibodies can be eliminated from ALS. After absorption anticomplementarity of ALS increases and the lymphocytotoxin titre declines. The optimal number of absorptions which would not reduce markedly the immunosuppressive activity of ALS remains to be determined.