Migration of people with Asian-type DEL to the United States. Conventional blood typing uses combinations of mouse monoclonal antibodies to detect the major Rh protein, “D,” by hemagglutination (A). Donors and patients with the Asian-type DEL mutation make multiple variants of the D protein in reduced amounts, which can be detected by eluting and concentrating the reagent antibodies from their cells and using them to agglutinate reagent RhD⁺ red blood cells (RBC) (B). Two million such individuals live in China, Japan, Korea, Thailand, and Burma, and tens of thousands live in other countries (C). Professional illustration by Somersault18:24.