Platelet alloimmunization after long-term red cell transfusion in transfusion-dependent thalassemia patients

The platelet (PLT) alloimminization status after long-term red cell (RBC) transfusion in thalassemia patients was investigated, including antibodies against HLA antigens and PLT-specific glycoprotein antigens.

Blood samples from a total of 60 thalassemia patients who routinely received washed RBCs were tested for the presence of HLA antibodies and PLT-specific glycoprotein antibodies with a commercial enzyme immunoassay kit. All patients were rescreened at a follow-up period of 12 to 15 months.

At the first year of study, 19 (31%) patients had HLA antibodies, 13 (22%) had HLA antibodies and PLT-specific antibodies, and 1 (2%) had PLT-specific antibodies. One patient showed weak reactive PLT autoantibody. The follow-up study showed that 7 patients developed HLA antibodies, whereas 1 patient lost HLA antibody activity. Nine patients developed new PLT-specific antibodies, yet 12 patients lost at least one of their PLT-specific antibodies.

Long-term RBC transfusions can induce PLT alloimmunization, both to HLA antigens and to PLT-specific antigens. The residual PLTs and white blood cells in RBC components could be the sources of immunization. In our thalassemia patients, HLA antibodies likely sustain longer than PLT-specific antibodies.