['Although infliximab treatment is an option for patients with ulcerative colitis (UC), not all patients do respond to therapy, and cellular mechanisms leading to therapy response are incompletely known.', 'The objective of this article is to determine early effects of infliximab therapy on T cells in the blood of UC patients and if effects differed in therapy responders and nonresponders.', 'Blood samples were obtained before and two weeks post-treatment start from 34 anti-tumor necrosis factor (TNF) therapy-naïve UC patients undergoing infliximab therapy. Response to therapy was evaluated prior to the fourth treatment dose. Expression of T cell surface markers and levels of soluble receptors and cytokines in serum were determined.', 'At baseline, there were no differences in cellular, biochemical or clinical parameters between therapy responders and nonresponders. Infliximab therapy reduced frequencies of CD25(+) T cells and increased frequencies of annexin V(+) T cells in patients responding to infliximab, but not in nonresponding patients, two weeks after therapy start. Only therapy responders had decreased serum levels of sCD25 and sTNFRII two weeks after treatment start. In contrast, clinical parameters did not reflect therapy outcome already two weeks after therapy start.'] Do cD25 and TNF receptor II reflect early primary response to infliximab therapy in patients with ulcerative colitis?