title: Gr-1+ myeloid cells derived from tumor-bearing mice inhibit primary T cell activation induced through CD3/CD28 costimulation.
abstract: Activation of T cells is a necessary step in the development of a specific antitumor immune response. In the present study, we evaluated the ability of Gr-1+ myeloid cells, derived from the bone marrow or spleen of tumor-bearing mice, to inhibit CD3/CD28-mediated T cell activation. Using flow cytometry, we found that growth of a murine colon carcinoma (MCA-26) induces a significant increase in the number of Gr-1+ and Gr-1+/Mac-1+ myeloid cells in both bone marrow and spleen of the tumor host. The proliferative response of T cells was dramatically decreased when naive T cells were activated by anti-CD3 and anti-CD28 Abs in the presence of a myeloid-enriched cell fraction derived from spleen or bone marrow of tumor-bearing mice vs the bone marrow of naive mice. Reversal of the inhibitory effect could be achieved by adding a combination of MnTBAP (manganese [III] tetrakis [4-benzoic acid]) porphyrin and l -NMMA (NG-monomethyl-l -arginine), a superoxide dismutase mimetic and inducible NO synthase inhibitor, respectively, or by depletion of the Gr-1-positive cells. IFN-gamma, which is endogenously produced by CD3/CD28-stimulated naive T cells, is involved in induction of the inhibitory activity of myeloid cells. Importantly, when T cells pre-activated with anti-CD3 Abs were used as responder cells, the bone marrow- or spleen-derived Gr-1+ myeloid cells were unable to suppress CD3/CD28-induced T cell proliferation. Our findings suggest that one mechanism by which an increased number of immune suppressive Gr-1+ cells can induce T cell unresponsiveness or immune tolerance in tumor hosts could be through peroxynitrite production upon primary T cell activation.
authors.affiliation: Institute for Gene Therapy and Molecular Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Kusmartsev
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: S H
authors.initials: SH
authors.lastname: Chen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D018106:CD28 Antigens / Q000502:physiology*; D017252:CD3 Complex / Q000276:immunology / Q000502:physiology*; D002452:Cell Count; D002455:Cell Division / Q000276:immunology; D002469:Cell Separation; D002478:Cells, Cultured; D018920:Coculture Techniques; D005260:Female; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D007108:Immune Tolerance / Q000187:drug effects; D007371:Interferon-gamma / Q000502:physiology; D007399:Interphase / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D016177:Macrophage-1 Antigen / Q000096:biosynthesis*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental / Q000276:immunology* / Q000473:pathology; D009566:Nitrates / Q000037:antagonists & inhibitors; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052247:Nitric Oxide Synthase Type II; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D018106:CD28 Antigens; D017252:CD3 Complex; D016177:Macrophage-1 Antigen; D009566:Nitrates; C039642:peroxynitric acid; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse