Proliferation of T-cell subsets. (A) Proliferation of total CD4+T cells in response to phyto-haemagglutinin (PHA) (2 μg/ml) in healthy control (HC) (n = 7, circles), active rheumatoid arthritis (RA) (RA, n = 5, diamonds) and in clinical remission (CR) (n = 11, triangles). Significantly better proliferation was observed in HC compared to active RA (P = 0.01) but not CR. A direct correlation was observed between proliferative responses of CD4+T cells and in vivo (serum) interleukin (IL)-7 (rho = 0.879, P <0.0001), combining all three groups. (B) Proliferation of effector T cells (CD4+CD25−) stimulated with PHA (2 μg/ml) in controls (n = 6, circles), active RA (RA, n = 5, diamonds) and CR (n = 8, triangles). Significantly better proliferation was observed in HC compared to RA (P = 0.003) and with CR (P = 0.001). A direct correlation was observed between serum IL-7 and effector cell proliferation (rho = 0.885, P <0.0001) combining the three groups.