Sensitization by platelet transfusion.

In patients without a history of previous blood transfusions or pregnancy, alloimmunization to HLA-antigens can be virtually prevented by rigorous white cell depletion of blood components. In the present state of knowledge it is recommended that white cells should be depleted prior to storage of blood and that "bedside" filtration should be omitted. Patients who are presensitized by past blood transfusions or pregnancy are still at considerable risk of activation of the secondary antibody response by HLA-class I antigens still present in white cell depleted blood components.