Patients who are transfused on multiple occasions with red cells or platelets may develop platelethyphen;reactive alloantibodies and experience decreased clinical responsiveness to platelet transfusion. This situation, conventionally described as ldquo;refractoriness to platelet transfusions,rdquo; is defimed by an unsatisfactory low posthyphen;transfusion platelet count increment. If antibodies to HLAs are detected, improved clinical outcomes may result from transfusions of HLAhyphen;matched or do norhyphen;recipient crossmatched platelets. Because refractoriness is an expected, frequently occurring phenomenon, prevention of HLA alloimmunization is an important management strategy. Prevention strategies include efforts to decrease the number of transfusions, filtration of cellular components to reduce the number of HLAhyphen;bearing leukocytes, or pretransfusion ultraviolet B irradiation of cellular components to decrease their immunogenicity. Other investigational approaches include reducing the expression of HLAs on transfused platelets, inducing a transient reticuloendothelial system blockade by infusions of specialized immunoglobulin products, or transfusing semisynthetic platelet substitutes lpar;thromboerythrocytes, thrombospheresrpar; or modified platelets lpar;infusible platelet membranes, lyophilized plateletsrpar;.
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