GBP1 and rheumatoid arthritis: Increased levels of CD64 are present on circulating CD1c+ cDC in patients with RA (Figure 1C and Supplemental Figure 2D), and expression of molecules associated with FcR-related signaling (SYK, GBP1, PLC, or PI3K) (40) were differentially affected on PB and SF CD1c+ cDC from RA subjects (Figure 6A and Supplemental Figure 4A).