Impact of TNF-α and LTα gene polymorphisms on genetic susceptibility in Indian SLE patients

Abstract

The promoter polymorphisms of tumour necrosis factor-α (TNF-α) and intronic Lymphotoxin-α (LTα) have been implicated as genetic risk factors for systemic lupus erythematosus (SLE) in various ethnic groups. The aim of this study was to investigate an impact of TNF-α (−308G/A; 238G/A) and LTα (+252A/G) gene polymorphisms in disease susceptibility among Indian 200 SLE patients along with 201 healthy controls. The gene polymorphisms were studied by using direct DNA sequencing and Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) methods. Serum levels were measured by multiplex assay. Allelic frequencies of TNF-α −308A (OR=2.3, p=0.0001, Pc=0.0003) and LTα +252G (OR=2.1, p<0.0001, Pc<0.001) were significantly higher in SLE patients. Frequency of haplotype-AGG was found to be higher in patients than controls (OR=12.2, p=0.0050). Serum levels of TNF-α and LTα also were found to be significantly higher in patients showing variant alleles. TNF-α −308G/A+A/A genotypes (p<0.01) and LTα +252 A/G+G/G genotypes (p<0.02) were significantly associated with renal disorders and haematological manifestations. SLE patients with −308G/A+A/A genotypes showed higher prevalence of anti-dsDNA antibodies (OR=3.9, p=0.0014, Pc=0.0098) and anti-Sm antibodies (OR=4.1, p=0.0002, Pc=0.0014). The present study suggests TNF-α −308A and LTα +252G as risk alleles for disease susceptibility associated with higher serum levels of TNF-α and LTα and concomitant discrete clinical features among Indian SLE patients.