title: In vitro immunoregulatory effects of thymoglobulin on human immune cell subpopulations.
abstract: Thymoglobulin (ATG) is a polyclonal rabbit antibody against human thymocytes used as a T cell-depleting agent in organ transplantation. Its polyclonal character suggests that its effect may go far beyond just T cell depletion. The aim of this study was to further elucidate possible mechanisms underlying the suppressive activity of ATG. For in vitro studies, human peripheral blood mononuclear cells (PBMC) were incubated with ATG or control Ig for various time points. Foxp3+regulatory cells (Tregs) and monocytes were phenotypically analyzed by flow cytometry and functionally tested by in vitro suppression assays. Cytokine levels were determined by quantitative RT- PCR, Multiplex or ELISA techniques. In vitro, the frequencies of Foxp3+Tregsincreased when human PBMC were stimulated with ATG as compared with stimulation by rabbit Ig or without stimulation. ATG-treated cells suppressed proliferation of autologous PBMC stimulated with anti-CD3 and anti-CD28 monoclonal antibodies and this suppression could be reversed by exogenous IL-2. The Foxp3+expression dropped down on day 10, which suggests that it is transient. Monocytes and natural killer cells stimulated with ATG down-modulated CD16. Monocytes suppressed the proliferation of autologous PBMC. However, there were not statistically significant differences in IL-10, TNF-α and TGF-β1 secretion by monocytes stimulated with ATG or control rabbit Ig. These findings suggest that ATG has immunomodulatory effects that go beyond T cell depletion and induction of Foxp3+Tregs. The induction of immunosuppressive monocytes might have a protective role in delaying transplant rejection.
authors.affiliation: Laboratory of Autoimmunity, Division of Experimental Pathophysiology and Immunology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Maja
authors.initials: M
authors.lastname: Buszko
authors.affiliation: Laboratory of Autoimmunity, Division of Experimental Pathophysiology and Immunology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Bojana
authors.initials: B
authors.lastname: Jakic
authors.affiliation: Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Innsbruck, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Ploner
authors.affiliation: Central Institute for Blood Transfusion & Immunological Department, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Paul
authors.initials: P
authors.lastname: Hoertnagl
authors.affiliation: Department of Internal Medicine III, Cardiology and Angiology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Christina
authors.initials: C
authors.lastname: Mayerl
authors.affiliation: Laboratory of Autoimmunity, Division of Experimental Pathophysiology and Immunology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Wick
authors.affiliation: Laboratory of Autoimmunity, Division of Experimental Pathophysiology and Immunology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria. Electronic address: giuseppe.cappellano@i-med.ac.at.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cappellano
mesh_terms: D000818:Animals; D000961:Antilymphocyte Serum / Q000494:pharmacology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism; D006801:Humans; D016130:Immunophenotyping; D007165:Immunosuppression Therapy; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007694:Killer Cells, Natural / Q000276:immunology*; D008212:Lymphocyte Depletion; D009000:Monocytes / Q000276:immunology*; D011817:Rabbits; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D000961:Antilymphocyte Serum; D016207:Cytokines; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D007166:Immunosuppressive Agents; C512542:thymoglobulin
keywords: ATG; Immunomodulation; Regulatory T cells; T cells