Protection of trinitrobenzene sulfonic acid-induced colitis by an interleukin 2-IgG2b fusion protein in mice

Background & Aims: We have shown in previous studies that an interleukin 2 (IL-2)-IgG2b fusion protein suppresses both humoral and cellular immune rea ctions in a murine model of DTH reaction. We now analyze the effects of IL- 2-IgG2b in a model of intestinal inflammation in mice induced by the hapten reagent 2,4,6-trinitrobenzene sulfonic acid (TNBS) that mimics immunologic characteristics of human Crohn's disease. Methods: In TNBS-induced colitis , colonic and splenic T-cell subsets were characterized by immunohistochemi stry and flow cytometry. Cytokine synthesis was studied by semiquantitative reverse-transcription polymerase chain reaction and intracellular cytokine staining in CD4(+) T cells. Results: When mice were treated with IL-2-IgG2 b, improvement in both wasting disease and histopathologic signs of colonic inflammation was observed. An increase in the number of colonic CD4(+)/CD2 5(+) T cells and increased synthesis of the immunosuppressive cytokine IL-1 0 also occurred. The protective role of IL-10 was demonstrated by the findi ng that neutralization of IL-10 in vivo using IL-10-specific antibodies inh ibited the IL-2-IgG2b effects in TNBS-induced colitis. Conclusions: These s tudies show for the first time that the IL-2-IgG2b fusion protein can abrog ate experimental colitis by local induction of IL-10-secreting T cells.