I am a high school student and I am a little confused that why only donor's antigen matters during blood transfusion? for e.g if the donor's blood is O- so it means that it will antibodies against all antigens so if he donated blood to say some A+ blood group then those antibodies will attack on that antigen and agglutination will occur, isn't it? At first I thought may be the antibodies do not work outside our body then later I heard of passive immunity so this thought is not correct then what's the correct reason?
Blood transfusions are done with erythrocyte concentrate and not whole blood. The antibodies are dissolved in the blood plasma. Grafting parts of the donor's immune system by transfusing white blood cells (the leukocytes) would cause even more problems than just agglutination in most cases. That's why care is taken to separate the red blood cells.