[Tumor necrosis factor alpha in systemic lupus erythematosus: evaluation by restriction fragment length polymorphism and production by peripheral blood mononuclear cells]

Abstract

Human TNF alpha locus locates between HLA-B and DR region on the short arm of chromosome 6. The 5.5 kb and 10.5 kb of TNF alpha restriction fragment length polymorphic (RFLP) bands were identified by Southern hybridization using a restriction enzyme, NcoI. The frequencies of those bands were not different among patients with systemic lupus erythematosus (SLE), those with rheumatoid arthritis and normal controls. In the lupus patients, proteinuria was more frequent in the patients with the 5.5 kb RFLP band (19/39: 48.7%) than those without 5.5 kb band (7/35: 20%) (p less than 0.05). Furthermore, this band was strongly associated with the haplotype HLA B44-DRw13-DQw1. In order to investigate the association between this gene polymorphism and the production of TNF alpha, peripheral blood mononuclear cells from patients with SLE and normal controls were cultured for 24 hours with lipopolysaccharide and concanavalin A and the amount of TNF alpha in the supernatant was measured by enzyme linked immunosorbent assay. The TNF alpha production of lupus patients was not statistically different from that of normal controls. The production of TNF alpha was not related to 5.5 kb RFLP band, but in the patients with SLE, the mean value of TNF alpha in patients with the 5.5 kb RFLP band tended to be higher than those without the band. Lupus patients were divided into two groups by the production of TNF alpha i.e. low TNF alpha inducibility group and high TNF alpha inducibility group. Patients with proteinuria were more frequent in patients of the high TNF alpha inducibility group than those of low TNF alpha inducibility group (p less than 0.05). There were four patients with HLA B44-DRw13-DQw1 who had the 5.5 kb RFLP band and three of them belonged to the high TNF alpha inducibility group with nephrosis. These data suggest that TNF alpha and HLA are possibly associated with the severity of lupus nephritis.