Hypomorphic C4B* 15 variant of the fourth component of complement.
We report a rare 'hypomorphic' C4 allotype detected during routine screening in controls for the Rogers:1 epitope. C4B* 15 was distinguished by having only faint staining when using polyclonal anti-C4 antibody on agarose immunoelectrophoresis (e.g. hypomorphic), having relatively weak hemolytic activity but being strongly reactive with monoclonal antibody to Rodgers 1. TaqI restriction fragment length polymorphism (RFLP) demonstrated that C4B* 15 segregated with 7 kb and 5.4 kb C4 gene fragments and with the haplotype HLA-A2,C-, B50,BW6,DR7,DQ2,DR52,SO7C2(1,15). The 5.4-kb fragment was more intense than the 7.0-kb fragment, suggesting duplication of the 5.4-kb fragment. This hypomorphic C4 allotype (genotype frequency = 0.0088) has diminished expression of C4 epitopes commonly recognized by polyclonal anti-C4 and may be missed by standard phenotyping methods.
Christenson
M J
MJ
Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
LaRosa
T
T
Jung
M
M
Bias
W B
WB
McLean
R H
RH
D000328:Adult; D015153:Blotting, Western; D015935:Complement C4b / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D004247:DNA / Q000032:analysis; D000939:Epitopes / Q000032:analysis; D005787:Gene Frequency; D006239:Haplotypes; D006801:Humans; D008297:Male; D010375:Pedigree; D012150:Polymorphism, Restriction Fragment Length
D000939:Epitopes; D015935:Complement C4b; D004247:DNA