Fig. S1.

(A) Overall experimental scheme. (B) Complete blood count of homozygous Kell-LPETG mice indicate normal RBC number, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin concentration (MCHC), hemoglobin content, and reticulocyte number. (C) Surface labeling of Kell-LPETG RBCs with GGG-biotin as characterized by flow cytometry. Because Kell protein is a RBC-specific protein, none of the other hematopoietic cell subsets, CD45⁺ cells, were sortagged with GGG-biotin. (D) No increase of Annexin V, a death cell marker, staining upon sortagging. (E) Benzidine staining reveals normal morphology of engineered RBCs. (Scale bars, 10 μm.)