A study by Reynolds et al. found that GM-CSF-producing T cells were significantly increased in RA synovial fluid, compared with synovial fluid from non-RA inflammatory arthritis, active RA peripheral blood and healthy donor peripheral blood.84 Furthermore, after co-cultured with CD4+ T cells in RA synovial fluid, but not healthy donor peripheral blood, a subpopulation of Mo differentiated into GM-CSF-dependent CD1c+ infDCs. Here, CD1C is linked to rheumatoid arthritis.