PTGDR2 and Arthritis: Of them, circulating fibroblasts (podoplanin<sup>+</sup>CD45<sup>-</sup>CD3<sup>-</sup>CD19<sup>-</sup>CD4<sup>-</sup>CD8<sup>-</sup>CD56<sup>-</sup>CD66b<sup>-</sup>CD294<sup>-</sup>) co-expressing CDH11 and C-C Chemokine Receptor 7 (CCR7) were found exclusively in arthritis patients' blood.