DAK, a new low-incidence antigen in the Rh blood group system

BACKGROUND: Some low‐incidence antigens in the Rh blood group system (e.g., VS, Rh32, FPTT) are expressed by more than one Rh complex. We describe a new low‐incidence antigen that is present on RBCs with the partial D phenotypes, DIIIa or DOL, on N RBCs and on one example of STEM+S RBCs. STUDY DESIGN AND METHODS: Standard hemagglutination testing was performed with two sera that agglutinated DIIIa RBCs on our in‐house antibody identification panel. DNA‐based assays were performed on selected samples. RESULTS: RBCs with the DIIIa (n = 31), DOL (n = 5), or N (n = 10) phenotype were agglutinated by both sera, as were RBCs from one STEM+S person. Reactivity with RBCs of either DIIIa or DOL phenotypes was stronger than with N RBCs and could not be separated by adsorption and elution. CONCLUSION: An antibody, anti‐DAK, which recognizes a novel low‐incidence antigen that is more strongly expressed on DIIIa and DOL RBCs than on N RBCs is described. The antibody agglutinated RBCs from 4 percent of D+ African American blood donors in New York. The antigen, DAK, has been assigned the ISBT number RH54 (004.054).