Six microsatellite markers on the short arm of chromosome 6 in relation to HLA-DR3 and TNF-308A in systemic lupus erythematosus.

Differences in allelic distribution at loci surrounding the human HLA-DRB1 and tumor necrosis factor (TNF) genes have been observed in association with systemic lupus erythematosus (SLE). We investigated whether the association of HLA-DRB1*0301 (HLA-DR3) and TNF-308A with SLE could be attributed to polymorphic markers in the chromosomal region encompassed by HLA-DRB1 and HLA-C. Ninety-one consecutive Caucasian patients with SLE and 253 controls (organ donors) were typed for HLA-DRB1, microsatellites D6S1014, D6S273, TNFa, MIB, C1_2_5, and C1_3_2 and the single nucleotide polymorphism at position -308 in the promoter of TNF. The independent contribution of alleles to disease susceptibility was estimated by cross-tabulation and multivariate logistic regression. Possession of TNF-308A was associated with susceptibility to SLE (odds ratio [95% confidence interval], 3.70 [2.24-6.11]). This remained present after stratification on possession of HLA-DR3 (pooled odds ratio, 2.53 [1.37-4.70]). Stratification revealed a possible association of possession of C1_2_5*192 with protection from SLE beyond the effects of HLA-DR3 and TNF-308A. A gene dosage effect was observed for -308A only (homozygotes, 7.75 [3.01-20.0], heterozygotes, 3.15 [1.85-5.37]). In multivariate analysis, possession of HLA-DR3, TNF-308A, and C1_2_5*192 remained independently associated with susceptibility to SLE (2.58 [1.29-5.18], 2.76 [1.43-5.31], and 0.26 [0.10-0.66], respectively). The association of possession of TNF-308A with susceptibility to SLE cannot be attributed to linkage to HLA-DR3 alone, nor to other polymorphic markers in the vicinity of the TNF gene. Further loci that are independently associated with SLE might be in the vicinity of marker C1_2_5.