title: A novel mechanism of action for anti-thymocyte globulin: induction of CD4+CD25+Foxp3+ regulatory T cells.
abstract: T cell-depleting agents are being tested as part of clinical tolerance strategies in humans with autoimmunity and transplantation. The immunosuppressive activity of anti-thymocyte globulin (ATG) has been thought to result primarily from depletion of peripheral lymphocytes. Herein is reported for the first time that ATG but not anti-CD52 mAb (alemtuzumab) or the IL-2R antagonists causes rapid and sustained expansion of CD4+CD25+ T cells when cultured with human peripheral blood lymphocytes. These cells display enhanced expression of the regulatory markers glucocorticoid-induced TNF receptor, cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), and forkhead box P3 and efficiently suppress a direct alloimmune response of the original responder lymphocytes. It is interesting that the cells do not suppress memory responses to the recall antigen mumps. Ex vivo expansion of regulatory T cells is due mainly to conversion of CD4+CD25- into CD4+CD25+ T cells and to a lesser degree to proliferation of natural CD4+CD25+ T cells. The induction of regulatory T cells depends on production of Th2 cytokines in the generating cultures. These novel data suggest that ATG not only may promote expansion/generation of regulatory T cells but also may be useful in future ex vivo expansion of these cells for cellular therapy in autoimmunity and clinical transplantation.
authors.affiliation: Brigham & Women's Hospital, Transplantation Research Center, EBRC, 221 Longwood Avenue, 3rd Floor, Boston, MA 02115, USA. nnajafian@rics.bwh.harvard.edu
authors.forename: Marta
authors.initials: M
authors.lastname: Lopez
authors.forename: Michael R
authors.initials: MR
authors.lastname: Clarkson
authors.forename: Monica
authors.initials: M
authors.lastname: Albin
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Sayegh
authors.forename: Nader
authors.initials: N
authors.lastname: Najafian
mesh_terms: D000961:Antilymphocyte Serum / Q000494:pharmacology*; D015704:CD4 Antigens / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors / Q000276:immunology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D053645:Interleukin-2 Receptor alpha Subunit / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism
chemical_list: D000961:Antilymphocyte Serum; D015704:CD4 Antigens; D016207:Cytokines; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D007166:Immunosuppressive Agents; D053645:Interleukin-2 Receptor alpha Subunit