The elucidation of a Kell-related autoantibody using ZZAP-treated red cells

A 61-year-old, nontransfused, Caucasian male was found to have a positive direct antiglobulin test (DAT) and an autoantibody in his serum prior to total hip replacement. Autoabsorption with the patient’s ZZAP-treated red cells failed to absorb the autoantibody, giving a clue to its possible specificity, which was subsequently found to be Kell-system related. In addition, his red cells were found to have a slightly weakened expression of Kell system antigens. The patient was fit and healthy with normal hematological indices at the time of the operation. One year later, the hematological findings remained the same despite the persistence of the autoantibody and a positive DAT. This suggested that the autoantibody was benign, which was supported by a negative in vitro macrophage assay.