CXCR4 and rheumatoid arthritis: In order to evaluate the chemokine receptor expression of these cells, we performed a SPICE algorithm flow cytometric analysis (39) of peripheral blood and synovial fluid RA and PsA patient CD14+ cell expression of the chemokine receptors CCR6, CCR7, CXCR3, CXCR4, and CXCR5 (Figure 2J and Supplementary Figure 3).