IL6 and rheumatoid arthritis: Leptin is elevated in the synovial fluid of RA and OA patients [49], and modulating leptin signalling through inhibition using an antisense oligonucleotide targeting the long leptin receptor isoform (OBRI) reduced leptin-mediated CXCL8 secretion and IL6 expression in OA synovial fibroblasts [118,119].