CD4 T cells derived from synovial fluid of rheumatoid arthritis patients are hyporesponsive upon (TSLP-primed) myeloid dendritic cell stimulation in contrast to peripheral blood-derived CD4 T cells. Thymic stromal lymphopoietin (TSLP)-primed myeloid dendritic cells (mDCs) from peripheral blood (PB) as well as both mDCs and TSLP-primed mDCs from synovial fluid (SF) of rheumatoid arthritis (RA) patients strongly activate PB-derived CD4 T cells, whereas SF-derived CD4 T cells are hyporesponsive upon (TSLP-primed) mDC activation. (A) mDC:T cell ratio 1:5, paired analysis of CD4 T cells and mDCs of a representative donor are shown. (B) mDC:T cell ratio 1:10 derived from PB of five RA patients. (C) mDC:T cell ratio 1:10 derived from SF of five RA patients. *P < 0.05 (statistically significant difference). CPM, counts per minute.