title: CD137 ligand signaling enhances myelopoiesis during infections.
abstract: CD137 and its ligand are expressed in the BM, and conflicting data exist on the regulation of myelopoiesis by the CD137 receptor-ligand system. CD137(-/-) mice have increased numbers of myeloid cells in the BM, indicating an inhibitory influence of CD137 on myelopoiesis. However, CD137 also induces proliferation of hematopoietic progenitor cells and their myeloid differentiation, arguing for an enhancing effect. Here we hypothesized that this latter case represents the situation during infections since expression of CD137 is activation dependent and strongly enhanced during inflammation. Indeed, infections with Influenza, Bordetella pertussis, Mycobacterium bovis, Bacille Calmette-Guérin or Escherichia coli or i.p. injection of LPS led to increased numbers of CD137-expressing cells, especially of CD4(+) T cells in the BM of mice. Coculture experiments confirmed that CD137 expression enables CD4(+) T cells to induce proliferation and myeloid differentiation of BM and hematopoietic progenitor cells. CD137 also enhances myelopoiesis in vivo since the infection-induced increase in myeloid cell proliferation and total myeloid cell numbers in the BM were significantly lower in CD137(-/-) mice. This study reconciles earlier conflicting data by demonstrating that while CD137-CD137L interactions inhibit myelopoiesis during steady-state conditions they increase myelopoiesis during infection.
authors.affiliation: Department of Physiology, National University of Singapore, Singapore.
authors.forename: Qianqiao
authors.initials: Q
authors.lastname: Tang
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Jiang
authors.forename: Sylvie
authors.initials: S
authors.lastname: Alonso
authors.forename: Aakansha
authors.initials: A
authors.lastname: Pant
authors.forename: Julia M
authors.initials: JM
authors.lastname: Martínez Gómez
authors.forename: David Michael
authors.initials: DM
authors.lastname: Kemeny
authors.forename: Lieping
authors.initials: L
authors.lastname: Chen
authors.forename: Herbert
authors.initials: H
authors.lastname: Schwarz
mesh_terms: D053330:4-1BB Ligand / Q000276:immunology / Q000378:metabolism; D000818:Animals; D001424:Bacterial Infections / Q000276:immunology*; D001853:Bone Marrow / Q000276:immunology / Q000382:microbiology / Q000821:virology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation; D002478:Cells, Cultured; D005260:Female; D006412:Hematopoietic Stem Cells / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000276:immunology; D038042:Myelopoiesis / Q000235:genetics / Q000276:immunology*; D009975:Orthomyxoviridae / Q000276:immunology*; D009976:Orthomyxoviridae Infections / Q000276:immunology*; D015398:Signal Transduction / Q000235:genetics; D053261:Tumor Necrosis Factor Receptor Superfamily, Member 9 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D053330:4-1BB Ligand; C505975:Tnfsf9 protein, mouse; D053261:Tumor Necrosis Factor Receptor Superfamily, Member 9