Development of alloanti-Jka in a patient with hemolytic anemia due to autoanti-Jkb

Autoanti-Jkb and a transient autoanti-E were identified in a patient with autoimmune hemolytic anemia, and red blood cells negative for Jkb and E antigens were transfused. Twelve weeks after transfusion, the autoantibody appeared to have developed broad specificity. However, autoadsorption studies revealed that the broad reactivity was due to the development of alloanti-Jka in addition to the autoanti-Jkb. Distinguishing this combination of alloanti-Jka plus autoanti-Jkb from an autoantibody with broad specificity will be important in selecting Jka antigen-negative red cells for subsequent transfusions. This case emphasizes the importance of additional serologic testing to detect alloantibodies in patients with broadly reactive warm autoantibodies.