Anti‐M causing delayed hemolytic transfusion reaction

Abstract
A 52‐year‐old gravida 1, para 1 woman with M‐ red cells experienced a delayed hemolytic transfusion reaction and exhibited an anti‐M antibody following the infusion of four units of M+ red cells. Measurements of erythrocyte survival using 51Cr‐labeled donor M+ and M‐red cells and in vitro studies of monocyte‐macrophage phagocytosis of sensitized reagent red cells implicate anti‐M in the pathogenesis of hemolysis.