Fig. 6.

(a) Levels of human endogenous retrovirus (HERV)-K (HML2) gag1 transcriptional activity after incubation with proinflammatory cytokines [interleukin (IL)-1β, IL-6 and tumour necrosis factor-α]. Cell lines incubated included fibroblast-like synoviocytes taken from rheumatoid arthritis (RA) patient, osteoarthritis patient (OA) and normal healthy door (NHD). (b) Levels of HERV-K (HML-2) gag1 after transfection of plasmids encoding Epstein–Barr virus gene products EBNA1 (Epstein–Barr nuclear antigen), LMP1 (late membrane protein 1) and LMP2A (late membrane protein 2a). Cell lines transfected included human fibroblast-like synoviocytes (HFLS) derived from an RA patient, HFLS taken from an OA patient and a healthy donor and a Hodgkin's lymphoma cell line (KMH2).