Red cell Rh antigen, Rh complex molecule, and Fy^b antigen expression of patients with spontaneous mixed RhD phenotype. (A) Double-color flow cytometric analyses of Rh antigen D, C, e, and c, total Rh protein, and RhAG expression of RBC samples from patient 3 and a D-positive (CcDdee) control are shown. Note presence of C⁺c⁺D⁺e⁺ and C⁻c⁺D⁻e⁺ RBC subpopulations. Similar results were obtained with samples from patients 1, 2, 4, and 6. (B) Double-color flow cytometric analysis of D and Fy^b antigen expression of patient 5 and a CcDdee, Fy(a⁺b⁺) control. Only the D-positive red cell subset of this patient is also Fy^b positive.