Partial expression of RHc on the RHD polypeptide

BACKGROUND: In the human Rh blood group system, c is, after D, the most immunogenic antigen. STUDY DESIGN AND METHODS: The background of a new partial c phenotype (Dc), identified on the RBCs of two unrelated white persons, was studied. This was done by analyzing the reactivity of the RBCs from the donors with anti‐c reagents, by performing sequence analysis, and by carrying out transduction studies. RESULTS: Serologic results suggested the existence of a new partial c phenotype. Genomic DNA and cDNA analysis revealed a normal RHCe allele, a normal RHD allele, and an RHD allele that carried two point mutations: 307T>C and 329T>C (the latter known to be associated with the DVII, Tar‐positive phenotype). No normal RHc allele was found. Thus, it was most likely that c is encoded by the mutated RHD allele (phenotype DDcCCee). Indeed, subsequent transduction of K562 erythroleukemic cells with an RHD cDNA carrying the 307T>C point mutation (leading to S103P) resulted in the expression of c. CONCLUSION: In the human Rh system, P103 is involved in the expression of c. Moreover, c can be expressed in vivo on the D polypeptide.