Cytokine-regulated expression of activated leukocyte cell adhesion molecule (CD166) on monocyte-lineage cells and in rheumatoid arthritis synovium

Objective, To determine whether monocyte/macrophage expression of the CD6 l igand, activated leukocyte cell adhesion molecule (ALCAM) (CD166), is regul ated by cytokines during inflammation in rheumatoid arthritis (RA), Methods, We used flow cytometry to test whether cytokines present in rheuma toid synovium could regulate ALCAM cell surface expression on peripheral bl ood (PB) monocytes and RA synovial fluid (SF) macrophages, and we examined ALCAM expression in situ in RA synovium by immunofluorescence. Results. The monocyte differentiation factors interleukin-3, macrophage col ony-stimulating factor (M-CSF), and granulocyte-macrophage colony-stimulati ng factor augmented ALCAM expression on PB monocytes, ALCAM was expressed o n monocyte-lineage cells in situ in inflamed synovium from patients with RA (9 of 9), but not in uninflamed synovium from patients with joint trauma ( 0 of 3), Furthermore, in vitro culture-induced ALCAM expression on PB monoc ytes and CD14+ RA SF cells was inhibited by an M-CSF neutralizing antibody. Conclusion. ALCAM expression on PB and SF monocytes/macrophages is enhanced by M-CSF.