CLINICAL-SIGNIFICANCE OF ANTI-AT-A

At-a is a high-frequency red blood cell (RBC) antigen. Anti-At-a has b een reported in rare At(a-) black subjects. We report two cases of ant i-At-a. A clinically significant anti-At-a was found in a 26-year-old black woman with systemic lupus erythematosus. The patient had a trans fusion reaction with chills and nausea during a RBC survival study, an d 95% of the radiolabeled At(a+) RBCs were destroyed within 3 h. A con currently performed monocyte monolayer assay was strongly reactive. An ti-At-a thus can cause rapid hemolysis of transfused RBCs, but At(a-) donor units are extremely scarce in rare donor registries. A second pa tient at our hospital had anti-At-a which did not affect her newborn. She also had autoimmune disease, insulin-dependent diabetes mellitus.