Signaling through Toll-like receptor-9 (TLR9), a mediator of innate immune responses, could have a role in the pathogenesis of systemic lupus erythematosus (SLE). Some studies have shown an association between polymorphisms in the TLR9 gene and disease manifestations. We investigated whether two single nucleotide polymorphisms (-1486 T>C and +1174 G>A) in the TLR9 gene are associated with the risk of renal involvement in SLE. DNA samples from 112 SLE patients (62 with lupus nephritis) and 100 healthy controls were obtained. TLR9 polymorphisms (-1486 T>C and +1174 G>A) were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Genotype and allelic frequencies were compared between lupus patients and healthy controls. Clinical and laboratory manifestations and activity scores on renal biopsy of patients with lupus nephritis were compared between various genotypes. There was no difference in the frequency of genotype or allele distribution at either of the two loci between lupus patients and controls and in lupus patients with or without nephritis. Patients with CC/CT genotype at the -1486 position had higher serum creatinine (P = 0.03) and Austin activity scores (P = 0.015). Patients with AA/AG genotype at +1174 position showed higher serum creatinine (P = 0.04), proteinuria (P = 0.011), anti-dsDNA titers (P < 0.001) and Austin activity scores (P = 0.003) than the GG genotype. Variations at the -1486 and +1174 positions of TLR9 gene are not associated with increased risk of SLE or that of kidney involvement in North Indians. CC/CT genotypes at -1486 and AA/AG at +1174 positions are associated with more severe kidney disease at presentation.
Keywords: Genetics; lupus nephritis; systemic lupus erythematosus; toll-like receptor.