HLA and Transfusion
The HLA class I antigens are carried in high concentration by leucocytes and platelets, but only in trace amounts on erytrocytes. Each transfusion of either platelets or leucocytes therefore carries a risk of immunizing the patient. Patients, with an intact immune system, who require multiple transfusions of whole blood, platelets or leucocyte concentrates, will therefore usually develop antibodies to HLA antigens. Anti-HLA antibodies may lead to two problems. Firstly, these patients become refractory to platelet transfusions, which they destroys rapidly, and secondly, non-haemolytic transfusion reactions may occur in response to HLA antigens.