Peripheral Blood from Rheumatoid Arthritis Patients Shows Decreased T(reg) CD25 Expression and Reduced Frequency of Effector T(reg) 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 (T(reg)) cells are thought to modulate the initiation and progression of RA, a consensus has yet to be reached regarding the function and composition of T(reg) cells in RA patients. To address these discrepancies, we analyzed not only the total T(reg) frequency but also that of T(reg) subpopulations in the peripheral blood of RA patients and healthy controls by flow cytometry. We found that the total T(reg) population was not significantly different between RA and control subjects. However, the effector T(reg) cell subgroup, defined as CD45RA(−)CD25(hi), showed markedly decreased frequency in RA patients. In addition, the total T(reg) population from RA patients showed a significant decline in the expression of CD25. Both the naïve and effector T(reg) subgroups also showed marked reduction of CD25 expression in RA patients compared to controls. These data suggest that the decreased frequency of effector T(reg) cells and overall reduction of CD25 expression in T(reg) cells in the peripheral blood may be evidence of altered T(reg) homeostasis associated with RA pathogenesis.