In Vivo Effects of Recombinant Human Interleukin-10 on Lymphocyte Phenotypes and Leukocyte Activation Markers in Inflammatory Bowel Disease

Background Interleukin-10 (IL-10) exhibits potent anti-inflammatory and immunosuppressive activities in vitro. Recent data indicate that treatment with recombinant human IL-10 (rHuIL-10) in Crohn's disease is safe and may induce clinical and endoscopic remission. The present study investigates the in vivo immunomodulatory properties of rHuIL-10 in inflammatory bowel disease (IBD). Methods As part of two randomized, double-blinded, placebo-controlled trials, repeated flow cytometric analyses of lymphocyte phenotypes (CD3, CD4, CD8, CD16+56, CD19) and activity markers (human leukocyte antigen [HLA]-DR; intercellular adhesion molecule-1 [ICAM-1]; IL-2 receptor α [IL-2Rα]; high affinity receptor for immunoglobulin G [IgG; FcγRI]) on T cells, monocytes, and neutrophils were performed in 17 patients with IBD who received rHuIL-10 (5, 10, or 20 µg/kg) or placebo, administered subcutaneously, once daily for 28 days. Results Minor changes were noted in CD3 + , CD8 + , and CD3 + /CD16 + 56 + lymphocyte phenotypes, whereas absolute numbers of CD4 + lymphocytes and CD19 + cells increased. T-cell activation markers HLA-DR and IL-2Rα were downregulated. rHuIL-10 did not influence HLA-DR expression on monocytes. ICAM-1 modulation on monocytes and neutrophils was mild and inconsistent. FcγRI expression was upregulated on both neutrophils and monocytes. Conclusions These data indicate that the immunosuppressive effects of rHuIL-10 treatment are partly different from its in vitro observed actions. The increase of the cytotoxicity-mediating FcγRI points to potential immunostimulating properties of this cytokine.