title: C4 and Bf phenotypes in black and Caucasian patients with childhood onset insulin dependent diabetes mellitus.
abstract: Certain alleles for the complement proteins, C4 and Bf, have been shown to be markers for insulin-dependent diabetes mellitus (IDDM) in samples of different racial and geographic composition. However, the same markers are not demonstrable in each group studied. Phenotyping for the complement alleles, C4 and Bf was performed on 168 Caucasian and 49 Black patients with IDDM. All of the patients were followed in Memphis, Tennessee and had onset of disease prior to age 18. The Bf*F1 allelic frequency was significantly increased for the Caucasian patients as compared to 93 healthy Caucasian controls (0.063 vs. 0.016) and for the Black IDDM patients as compared to 43 healthy Black controls (0.102 vs. 0.035). C4 phenotype frequencies showed a significant increase of the C4AQ0 (rr = 2.13) and C4A4 (rr = 2.91) phenotypes for the Caucasian IDDM patients as compared to controls, but the frequency of homozygous null C4A was not significantly increased. In addition significant negative associations of IDDM with C4A3 and C4A6 phenotypes and no association with any C4B phenotype were observed in our Caucasian patient population. Our data for Mild-South Blacks with IDDM suggest a similar positive association of IDDM with the BfF1 phenotype (rr = 3.4). However, there was no evidence among Black IDDM patients of the C4AQ0 and C4A4 associations observed in the Caucasian sample. The data support a possible association of IDDM with the C4A2 (rr = 5.86) and C4B2 (rr = 5.26) phenotypes. The hypothesis that racial admixture may account for the higher frequency of IDDM in US Blacks as compared with African Blacks has been forwarded by others.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, University of Tennessee, Memphis.
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: M L
authors.initials: ML
authors.lastname: Rivas
authors.forename: G A
authors.initials: GA
authors.lastname: Burghen
authors.forename: E C
authors.initials: EC
authors.lastname: Hudson
authors.forename: R J
authors.initials: RJ
authors.lastname: Wyatt
mesh_terms: D000483:Alleles; D044383:Black People / Q000235:genetics; D002648:Child; D003181:Complement C4 / Q000235:genetics*; D011415:Complement Factor B / Q000235:genetics*; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics / Q000276:immunology*; D004792:Enzyme Precursors / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D005819:Genetic Markers; D006801:Humans; D008297:Male; D010641:Phenotype; D044465:White People / Q000235:genetics
chemical_list: D003181:Complement C4; D004792:Enzyme Precursors; D005819:Genetic Markers; D011415:Complement Factor B