RESUMEN
A reduced frequency of HLA-DQ6 in patients with a positive direct antiglobulin test (DAT) was previously reported but race was undisclosed. Therefore, we investigated a total of 275 patients (80 Caucasian, 113 African American, and 82 Mexican American) and 518 normal controls (205 Caucasian, 208 African American, and 105 Mexican American). These were typed for class II HLA antigens using molecular techniques. A DAT was performed on each patient's red cells drawn into EDTA using both mouse and rabbit polyspecific reagents. Of 275 patients tested, 73 (27%) had a positive DAT (12 Caucasians, 35 African Americans, and 26 Mexican Americans). We found that 5 (42%) Caucasian patients and 103 (50%) Caucasian controls possessed the DQB*06 allele (p =.56). In the African American group, 15 (43%) patients and 91 controls (44%) were DQB*06 positive (p =.92). Six Mexican American patients (23%) and 21 controls (20%) had the DQB*06 allele (p =.72). This article underscores the need to use race-matched controls when genetic disease associations are sought.
RESUMEN
Few data exist on associations of class II and class III alleles of the major histocompatibility complex (MHC) and susceptibility to systemic lupus erythematosus (SLE) in Mexican Americans, a group of predominantly mixed Spanish and Native American ancestry. Therefore, MHC class II alleles (HLA-DRB1, DQA1, DQB1, DPA1 and DPB1 alleles) and C4 allotypes were determined in 52 Mexican American SLE patients and 105 ethnic-matched controls. HLA-DRB1*0301 and C4A*Q0 were each increased in the SLE patients, especially HLA-DRB1*0301 in those with anti-Ro/SSA autoantibodies. C4A*Q0 was associated with HLA-DRB1*0301 only in a minority of patients and controls. Anti-U1RNP antibodies were significantly associated with the presence of HLA-DQB1*0302, and the risk for the production of anti-Ro antibodies was heightened by the presence of at least three (out of four possible) DQA1 chains possessing a glutamine at position 34 and/or DQB1 chains a leucine at position 26 of their outermost domains. Thus the HLA class II and C4 null allele associations that have been noted in other ethnic groups are also found in Mexican Americans, suggesting shared susceptibility factors across ethnic lines in predisposition to SLE.
Asunto(s)
Alelos , Complemento C4/genética , Genes MHC Clase II , Antígenos HLA-D/genética , Lupus Eritematoso Sistémico/genética , Americanos Mexicanos/genética , Autoanticuerpos/análisis , Secuencia de Bases , Susceptibilidad a Enfermedades/etnología , Frecuencia de los Genes , Predisposición Genética a la Enfermedad , Haplotipos/genética , Humanos , Indígenas Norteamericanos/genética , Desequilibrio de Ligamiento , Lupus Eritematoso Sistémico/etnología , Lupus Eritematoso Sistémico/inmunología , Datos de Secuencia Molecular , España/etnologíaRESUMEN
Dia occurs with a frequency of 8.2 to 14.7 percent in Mexican-Americans living in three Texas communities. Of 4225 blood samples tested, only six (0.14%) were Di(a+b-), and none of 2540 samples was Di(a-b-). In other studies, 1 of 525 random white blood donors was Di(a+), and Dib was well developed in 100 random umbilical cord blood samples.