CD34 and rheumatoid arthritis: They observed a higher proportion of the second THY1+ CD34− HLA-DRhigh population in RA with increased expression of major histocompatibility complex (MHC) class II, collagens, the interferon (IFN)-γ signaling, IL-6, CCL2, and CXCL12, indicating that these cells are in an active cytokine-producing state (55).