title: DNA sequence analysis of the C4 antigen WH: evidence for two mechanisms of expression.
abstract: Amino acid and protein analyses have allowed the construction of a model for the C4-based Rodgers and Chido blood group antigens. The single low-frequency allele (WH) in this blood group system, however, has not been characterized at the molecular level. Two WH+ donors were studied by C4 agarose gel electrophoreses, immunoblot studies using monoclonal anti-Rg: 1 or anti-Ch: 1, serological phenotyping, polymerase chain reaction-restriction fragment length polymorphism of their C4 genes, and DNA sequencing of the WH allele. The first donor had the C4A1, A3 phenotype; the C4A1 carried Ch: 1, 3, 6 (thus exhibiting reversed antigenicity) and the C4A3 carried the WH antigen. The amino acid sequence of the WH allele was PCPVLD at positions 1101 - 1106, S at position 1157, and VDLL at positions 1188 - 1191. A second donor typed as C4A2, A4, B1 and was also WH+. Immunoblot analysis showed that a C4B1 protein expressed Rg: 1. Sequence analysis of the C4B genes showed the amino acids LSPVIH at positions 1101 - 1106, S at position 1157, and ADLR at positions 1188 - 1191. Thus, the WH antigen is a conformational epitope that can arise through different mechanisms on either a C4A or C4B gene.
authors.affiliation: Division of Rheumatology and Clinical Immunogenetics, Department of Internal Medicine, University of Texas-Houston Medical School, 6431 Fannin, Houston, TX 77030, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Moulds
authors.forename: S L
authors.initials: SL
authors.lastname: Roberts
authors.forename: T D
authors.initials: TD
authors.lastname: Wells
mesh_terms: D000483:Alleles; D001483:Base Sequence; D001789:Blood Group Antigens / Q000235:genetics*; D003181:Complement C4 / Q000235:genetics*; D004247:DNA / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D012150:Polymorphism, Restriction Fragment Length
chemical_list: D001789:Blood Group Antigens; D003181:Complement C4; D004247:DNA