Similar to what we have seen in immune cells [17–21], our results show that PKD1 can be activated in human primary FLS (HFLS-N and HFLS-RA) in response to TLR/IL-1R ligands, and that PKD1 plays an essential role in the TLR/IL-1R-mediated expression of proinflammatory mediators in both HFLS-N and HFLS-RA. Here, PKD1 is linked to rheumatoid arthritis.