Peripheral Blood from Rheumatoid Arthritis Patients Shows Decreased Treg CD25 Expression and Reduced Frequency of Effector Treg Subpopulation.

Rheumatoid arthritis (RA) is a common autoimmune disease characterized by immune cell infiltration of the synovium, leading to the loss of cartilage, bone, and joint function. Although regulatory T (Treg) cells are thought to modulate the initiation and progression of RA, a consensus has yet to be reached regarding the function and composition of Treg cells in RA patients. To address these discrepancies, we analyzed not only the total Treg frequency but also that of Treg subpopulations in the peripheral blood of RA patients and healthy controls by flow cytometry. We found that the total Treg population was not significantly different between RA and control subjects. However, the effector Treg cell subgroup, defined as CD45RA-CD25hi, showed markedly decreased frequency in RA patients. In addition, the total Treg population from RA patients showed a significant decline in the expression of CD25. Both the naïve and effector Treg subgroups also showed marked reduction of CD25 expression in RA patients compared to controls. These data suggest that the decreased frequency of effector Treg cells and overall reduction of CD25 expression in Treg cells in the peripheral blood may be evidence of altered Treg homeostasis associated with RA pathogenesis.