@article {Sicat1821, author = {Jocelyn Sicat and Natalie Sutkowski and Brigitte T Huber}, title = {Expression of human endogenous retrovirus HERV-K18 superantigen is elevated in juvenile rheumatoid arthritis.}, volume = {32}, number = {9}, pages = {1821--1831}, year = {2005}, publisher = {The Journal of Rheumatology}, abstract = {OBJECTIVE: To investigate the presence of a host-encoded superantigen as possible etiologic factor in pediatric rheumatic disease. We measured the expression and the ability of interferon-alpha (IFN-alpha) to induce the human endogenous retrovirus HERV-K18 superantigen in juvenile rheumatoid arthritis (JRA) and pediatric systemic lupus erythematosus (SLE). METHODS: Expression levels of HERV-K18 were measured in peripheral blood or synovial fluid mononuclear cells (SFMC) from 13 patients with JRA, 11 pediatric SLE patients, and 24 healthy controls, by semiquantitative reverse transcription-polymerase chain reaction, comparing 18S ribosomal transcripts as endogenous standard. IFN-alpha induction was tested by pretreatment of samples with 2000 U/ml. RESULTS: HERV-K18 expression was significantly elevated in peripheral blood from patients with JRA (mean ratio of HERV-K18 to 18S ribosomal transcripts 2.456, SD 2.122; p = 0.014), but not patients with SLE (mean 0.997, SD 0.579; p = 0.258), compared to controls (mean 0.749, SD 0.598). HERV-K18 transcripts were detected in SFMC of 7/7 JRA patients. IFN-alpha induced HERV-K18 strongly in JRA (mean fold induction = 8.934, SD 15.556) and controls (mean 8.270, SD 6.609), but weakly in SLE (mean 2.432, SD 2.219; p = 0.009). HERV-K18 levels were found to be independent of previously determined modifiers of expression, including Epstein-Barr virus infection, IFN-alpha levels, or the percentage of B cells in peripheral blood. CONCLUSION: HERV-K18 superantigen levels were elevated in JRA patients, but not pediatric patients with SLE, suggesting a possible mechanism for autoimmunity in the former group by superantigen stimulation of autoreactive T cells.}, issn = {0315-162X}, URL = {https://www.jrheum.org/content/32/9/1821}, eprint = {https://www.jrheum.org/content/32/9/1821.full.pdf}, journal = {The Journal of Rheumatology} }