text: Altered memory T cell differentiation in patients with early rheumatoid arthritis. 
  The chronic immune response in rheumatoid arthritis (RA) might be driven by activated Th1 cells without sufficient Th2 cell differentiation to down-modulate inflammation. To test whether disordered memory T cell differentiation contributes to the typical Th1-dominated chronic inflammation in RA we investigated differentiation of resting CD4+ memory T cells in patients with early (6 wk to 12 mo) untreated RA and in age- and sex-matched healthy controls in vitro. No difference in cytokine secretion profiles of freshly isolated memory T cells was detected between patients and controls. A cell culture system was then employed that permitted the differentiation of Th effectors from resting memory T cells by short term priming. Marked differences were found in response to priming. Th2 cells could be induced in all healthy controls by priming with anti-CD28 in the absence of TCR ligation. By contrast, priming under those conditions resulted in Th2 differentiation in only 9 of 24 RA patients. Exogenous IL-4 could overcome the apparent Th2 differentiation defect in seven patients but was without effect in the remaining eight patients. In all patients a marked decrease in IL-2-producing cells and a significant increase in well-differentiated Th1 cells that produced IFN-gamma but not IL-2 were evident after priming with anti-CD3 and anti-CD28. The data suggest that CD4+ memory T cells from patients with early untreated RA manifest an intrinsic abnormality in their ability to differentiate into specific cytokine-producing effector cells that might contribute to the characteristic Th1-dominated chronic (auto)immune inflammation in RA. 