Fig. 5

Impact of proteoglycan-4 (PRG4) immunoprecipitation on activation of toll-like receptors 2 and 4 (TLR2 and TLR4) expressing human embryonic kidney (TLR2-HEK and TLR4-HEK) cells by pooled osteoarthritis (OA) (n = 5) and pooled rheumatoid arthritis (RA) (n = 5) synovial fluid (SF). OA or RA SF with or without PRG4 immunoprecipitation were incubated with TLR2-HEK or TLR4-HEK cells (0.5, 3.75, 5.0 and 10.0 % dilution) at 37 °C for 24 h. The 630 nm absorbance values across experimental groups were normalized to untreated controls. Data represent the mean ± SD from three independent experiments. a Impact of PRG4 immunoprecipitation on TLR2 activation by OA SF. TLR2 activation was significantly higher in PRG4-immunoprecipitated OA SF (OA SF (-PRG4)) compared to OA SF at 3.75, 5.0 and 10.0 %; *p <0.001. b Impact of PRG4 immunoprecipitation on TLR2 activation by RA SF. TLR2 activation was significantly higher in PRG4 immunoprecipitated RA SF (RA SF (-PRG4)) compared to RA SF at 5 and 10 %; *p <0.001. c Impact of PRG4 immunoprecipitation on TLR4 activation by OA SF and RA SF. There was no significant difference in TLR4 activation between OA SF and OA SF following PRG4 immunoprecipitation (OA SF (-PRG4)) across any SF dilutions. There was no significant difference in TLR4 activation between RA SF and RA SF following PRG4 immunoprecipitation (RA SF (-PRG4)) across any SF dilutions