Association between HL‐A and Red Cell Antigens

Two sera with cytotoxic anti‐HL‐A2 antibodies and haemagglutinins reacting preferably with red cells from HL‐A28‐positive2 donors, have been absorbed with several white and red cells. Both cytotoxic and haemagglutinating antibodies are shown to cross‐react with the two antigens. Absorption experiments have also been carried out in two sera with cytotoxic anti‐HL‐A8 activity and haemagglutinins. The results indicate that both the haemagglutinating and the cytotoxic antibodies are directed against the HL‐A8 antigen. The titration and absorption results show that the haemagglutinins are rather abundant in the sera, while the antigenic sites on the red cells are apparently very few.