IL1R1 and rheumatoid arthritis: Although HFLS-RA used in this study showed the higher levels of PKD1 phosphorylation in unstimulated, as well as TLR/IL-1R ligand-stimulated, condition compared to those in HFLS-N used in this study, this does not necessarily indicate that PKD1 is hyper-activated in FLS in RA because a single patient sample from each group were utilized in this study.