To evaluate the responsiveness of RA CD4+ T cells to IL-10, purified PB CD4+ T cells from three patients with active RA and from three healthy controls were stimulated by immobilized anti-CD3 antibody and anti-CD28 antibody with or without diluted concentrations of IL-10 for 36 hours, and IFN-γ production was measured by ELISA. Here, CD4 is linked to rheumatoid arthritis.