Boirivant M, Marini M, Di Felice G, et al. info however, disappointingly little is found within the mechanisms of action of infliximab. Almost invariably the optimism caused by the feeling of finally having found out a magic bullet against unyielding diseases causes all interest and resources to be shifted to more medical tests. Although this reaction is understandable, all too often it comes at the expense of investigating mechanisms of action that would ultimately lead to a safer and more reliable use of the biological agent, or actually the finding of better biologicals. Therefore the study of ten Hove in this problem of hypothesised that infliximab, in addition to neutralising soluble TNF-, could improve Crohn’s Oxytetracycline (Terramycin) disease by inducing apoptosis of mucosal T cells.3 To test this hypothesis, the authors measured markers of activation and cell death in peripheral and mucosal T cells of patients with clinically active Crohn’s disease receiving a therapeutic infusion of infliximab. In individuals with a medical response they found only minor changes in the properties and apoptosis of circulating T cells while the quantity of apoptotic cells, primarily CD3+ T cells, significantly CD209 improved in mucosal biopsies taken 24 hours after the start of treatment. They complemented these observations by demonstrating that infliximab could induce in vitro apoptosis of triggered but not resting Jurkat T cells. As mucosal T cells in active Crohn’s disease are in an enhanced state of activation, the authors concluded that the beneficial effects of infliximab may be mediated by killing of triggered mucosal T cells (fig 1 ?). This summary is warranted even though in vitro studies on infliximab mediated apoptosis of resting and triggered peripheral blood and lamina propria T cells were not performed. The results could have reinforced the conclusion reached from the authors, and shed some light on whether defective apoptosis in Crohn’s disease is an intrinsic systemic defect or one that is only detectable on exposure of T cells to the immunological difficulties of the mucosa.15 A number of interesting issues, questions, and speculations are raised by this work. For starters, as ten Hove point out, the exact mechanism of infliximab mediated killing of mucosal T cells remains to be explored, especially realizing that apoptosis is not induced by direct in vitro exposure of these cells to TNF-.10 Is induction of mucosal T cell apoptosis the only mechanism responsible for the beneficial effects of infliximab? Most likely not in view of the multiplicity of biological activities of TNF- and this antibody.4,5 Whether induction of apoptosis is the dominant mechanism of action should be ascertained in the near future once studies similar to the one reported in this problem of are repeated in other diseases that also benefit from TNF- blockade. Finally, if indeed killing of triggered T cells is the of infliximab, this could possess broad restorative implications. In fact, any condition characterised by improved numbers of triggered T cells may profit from killing of these cells in the affected organs. There is preliminary evidence that infliximab provides medical benefit for some individuals with steroid refractory ulcerative colitis,16 which is also characterised by high numbers of triggered T cells in the mucosa. Development of the ten Hove study to ulcerative colitis and additional chronic inflammatory conditions should provide rather interesting answers to the questions and speculation raised with this commentary. Referrals 1. Elliott MJ, Maini Oxytetracycline (Terramycin) RN, Feldmann M, et al. Randomised double-blind assessment of chimeric monoclonal antibody to tumour necrosis element (cA2) versus placebo in rheumatoid arthritis. Lancet 1994;344:1105C10. [PubMed] [Google Scholar] 2. Targan SR, Hanauer SB, vehicle Deventer SJH, et al. A short-term study of chimeric monoclonal antibody cA2 to tumor necrosis element for Crohn’s disease. N Engl J Med 1997;337:1029C35. [PubMed] [Google Scholar] 3. ten Oxytetracycline (Terramycin) Hove T, vehicle Montfrans C, Peppelenbosch MP, et al. Infliximab treatment induces.