Allo-anti-Chido in a Ch-positive patient

Allo-anti-Chido (Ch) was detected in a patient whose red cells typed as Ch+. The C4 allotype of the patient was A4,B2 which associates strongly with the Ch phenotype Ch:1,-2,3,4,-5,6. Anti-Ch2 + Ch5 were the Ch specificities identified. Absence of only Ch2 and Ch5 determinants on the C4B protein allowed this unique immune response to blood transfusion.