Association of tumor necrosis factor receptor type II polymorphism 196R with systemic lupus erythematosus in the Japanese - Molecular and functional analysis

Objective. To investigate whether a polymorphism(s) or mutation(s) in the t umor necrosis factor receptor II (TNFRII) gene is involved in the pathogene sis of Systemic lupus erythematosus (SLE). Methods. All 10 exons of the TNFRII gene were analyzed by exon-specific pol ymerase chain reaction-single-strand conformation polymorphism, followed by nucleotide sequencing of exons that displayed aberrant bands. To analyze t he function of the TNFRII polymorphisms, the full-length TNFRII complementa ry DNA of each allele was transfected in HeLa cells and then studied for sp ecific binding of I-125-TNF alpha, as well as interleukin-6 (IL-6) producti on and cytotoxic activity after treatment with recombinant human TNF alpha. Results. We identified 4 polymorphisms, at codons 56, 181, 196, and 232. Th e latter 2 had amino acid substitutions M196R and E232K, respectively. Only the 196R allele was significantly associated with SLE in our 105 Japanese SLE patients, with an allele frequency of 20.5%, compared with 12.6% in 99 healthy controls (P = 0.0335). More importantly, using TNFRII-transfected H eLa cells, we demonstrated significantly increased IL-6 production by 196R TNFRII compared with 196M TNFRII. The cytotoxic activity induced by 196R TN FRII was also increased compared with that of 196M TNFRII This increase was achieved without affecting the binding affinity of TNF alpha to TNFRII, as demonstrated by the finding that specific TNF alpha binding to the HeLa tr ansfectants of 196R and 196M TNFRII was similar, with K-d values of 3.12 x 10(-10)M and 4.34 x 10-10M, respectively. Conclusion. These results suggest that 196R TNFRII, which transduces the si gnals of TNF alpha more effectively than does 196M TNFRII, is involved in t he pathogenesis of SLE.