Alloantibody responses in multiply transfused sickle cell patients

Fifty-six adult and 15 pediatric black patients with sickle cell disease were studied to determine their antibody responses to repeated transfusions of red cells. Red cell antibodies were determined retrospectively; anti-lymphocyte antibodies (class I and II) were determined on the single, most recently drawn blood sample. All adults were HLA-A, B, C, DR and DQ typed. Ten percent of the individuals with less than 50 transfusions, but greater than 50% with 100 transfusions or more, had red cell antibodies. The percentage of patients producing anti-red cell antibodies increased consistently with the number of transfusions (p = 0.0062). Women were more likely to become sensitized to red cell antigens than men (p = 0.008), and nulliparous women more likely than multiparous women. Children were also sensitized to red cell antigens (20%), and to a high degree to lymphocyte antigens (73%). No HLA association was found with increased propensity to red cell sensitization. A weak association of HLA DR5 and DR7 with failure to become sensitized to lymphocyte alloantigens was observed, but did not reach statistical significance. Our results suggest that, while genetic factors influencing transfusion response almost certainly exist, other factors such as number of transfusions, age, sex and parity need to be examined to provide accurate projections of risk in chronic transfusion.