Platelet Antigens and Antiplatelet Antibodies

Transfusion of allogenic platelets (TAP) is a potent therapeutic method for patients with impaired bone marrow platelet-producing function caused by endogenous depression ofhemopoiesis or exogenous factors, such as radiation or cytostatic therapy. Transplantation of allogenic bone marrow from close relatives is impossible without TAP. Allogenic platelets are required for recipients in whom thrombopoiesls in the bone marrow ceases because of fractionated irradiation and cytostatic therapy, while transplanted cells do not yet function. TAP is an expensive procedure. It costs at least $500 to attain a hemostatic effect by means of TAP in one patient. That is why it is particularly disappointing when platelet transfusion is ineffective because of immunological reasons which have been neglected by transfusiologist [ 1,2]. Immune conflict in TAP can be due to allosensitization caused by previous pregnancies and transfusion of blood components [2,10,1 l]. The conflict consists in rejection of donor platelets because of immune antibody production in the recipient. It considerably reduces the efficiency of therapy and even annihilate its therapeutic effect. The immune reaction can be associated with fever (nonhemolytic transfusion reaction) and the absence of increment in platelets count (refraction to platelet transfusion. RPT). The main cause of immune complications in TAP are antibodies to HLA class I antigens expressed on T lymphocytes, polymorphonuclear leukocytes, and platelets [8,9]. It is believed that the more blood component transfusions (erythrocyte and platelet transfusions) are received by patients, the higher the incidence of antibody production and RPT [6]. Sensitizing doses for leukocytes and platelets are 15x10 s and