title: Quantitative and antigenic differences in complement component C4 between American blacks and whites.
abstract: A population of 98 healthy Black Americans was studied in order to determine normal ranges for total C4, C4A and C4B. Mean total C4 in Blacks measured by an enzymelinked immunoassay (EIA) was 44 +/- 12.8 mg/dl which was significantly different (p less than 0.001) from Caucasian levels of 31.7 +/- 11.5 mg/dl. The difference in total C4 was due to increased levels of C4B in Blacks (means = 24.4 mg/dl) as compared to Whites (means = 15.7 mg/dl; p less than 0.001). These results remained significantly different even when 8 samples having the C4A 91 phenotype were excluded. Since EIAs using monoclonal antibodies with Ch 1 specificity may yield false results, C4 allotyping is recommended when quantitating C4A and C4B levels in Blacks.
authors.affiliation: Division of Rheumatology and Clinical Immunogenetics, University of Texas Health Science Center, Houston.
authors.forename: J M
authors.initials: JM
authors.lastname: Moulds
authors.forename: N B
authors.initials: NB
authors.lastname: Warner
authors.forename: F C
authors.initials: FC
authors.lastname: Arnett
mesh_terms: D000483:Alleles; D044383:Black People; D003181:Complement C4 / Q000032:analysis* / Q000235:genetics*; D015934:Complement C4a / Q000032:analysis / Q000235:genetics; D015935:Complement C4b / Q000032:analysis / Q000235:genetics; D005787:Gene Frequency; D006801:Humans; D005779:Immunodiffusion; D007124:Immunoenzyme Techniques; D011110:Polymorphism, Genetic; D014481:United States; D044465:White People; D001741:Black or African American
chemical_list: D003181:Complement C4; D015934:Complement C4a; D015935:Complement C4b