title: A strong association between null alleles at the C4A locus in the major histocompatibility complex and systemic sclerosis.
abstract: Allotyping of the major histocompatibility complex (MHC)-linked complement component C4 has revealed a strong association of the null allele, C4A*Q0, with systemic sclerosis (SSc). Sixty-four percent of patients with SSc carried the C4A*Q0 allele, compared with 17% of the control group. Twenty-five patients and their families were typed for HLA antigens (A, B, Cw, and DR) and the MHC-linked complement components C4 and factor B to identify haplotypes in the MHC linkage group and C4 null alleles. Strong allelic association of HLA-B8 and DR3 with C4A*Q0 probably explains the previously reported association of SSc with the extended haplotype carrying HLA-B8 and DR3. Ninety-two percent of the patients had either C4A*Q0 or DR5; 31% of the controls had either C4A*Q0 or DR5.
mesh_terms: D000483:Alleles; D006680:HLA Antigens / Q000235:genetics; D015795:HLA-B8 Antigen; D006684:HLA-DR Antigens / Q000235:genetics; D015803:HLA-DR3 Antigen; D006801:Humans; D008285:Major Histocompatibility Complex; D012595:Scleroderma, Systemic / Q000235:genetics*
chemical_list: D006680:HLA Antigens; D015795:HLA-B8 Antigen; D006684:HLA-DR Antigens; D015803:HLA-DR3 Antigen