title: The spleen dictates platelet destruction, anti-platelet antibody production, and lymphocyte distribution patterns in a murine model of immune thrombocytopenia.
abstract: For many years, splenectomy has been used to treat immune thrombocytopenia (ITP), and this procedure benefits approximately two-thirds of the treated patients. Although splenectomy may raise platelet counts, antibody-coated platelets and cytotoxic T lymphocytes appear to persist or can change over time. To better understand how the spleen may affect anti-platelet immune responses, we used a murine model of ITP demonstrating both antibody-mediated and T lymphocyte-mediated thrombocytopenia. Mice with severe combined immunodeficiency (SCID) were either splenectomized or not and transfused with splenocytes from CD61 (GPIIIa) knockout mice immunized against CD61(+) platelets. Platelet counts and anti-platelet antibody levels were performed weekly. After 4 weeks, the mice were sacrificed, and lymphoid organs were harvested and examined by flow cytometry to quantify CD4(+)CD25(+)FoxP3(+) Tregs and conventional cross-presenting XCR1(+) and tolerizing SIRPα+ dendritic cells. The results indicate that compared with control non-splenectomized mice, thrombocytopenia was improved and anti-platelet antibody production was significantly diminished in all splenectomized mice that received immune splenocytes. Splenectomized SCID mice also had a marked reduction in Tregs in the thymus together with an increased proportion of both thymic dendritic cell subsets that correlated with increased platelet counts. Of interest, although splenectomy diminished anti-platelet antibody production and raised platelet counts, marrow megakaryocyte densities were still significantly reduced in mice that received immune splenocytes. These results suggest that the spleen in murine ITP not only is the primary site responsible for platelet destruction, but it also controls, to a significant extent, the antibody response against platelets and the migration patterns of lymphocyte subsets.
authors.affiliation: Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Rukhsana
authors.initials: R
authors.lastname: Aslam
authors.affiliation: Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Canadian Blood Services, Toronto, ON, Canada.
authors.forename: Rick
authors.initials: R
authors.lastname: Kapur
authors.affiliation: Division of Hematology and Department of Medicine, University of Rochester, Rochester, NY.
authors.forename: George B
authors.initials: GB
authors.lastname: Segel
authors.affiliation: Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Li
authors.initials: L
authors.lastname: Guo
authors.affiliation: Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Anne
authors.initials: A
authors.lastname: Zufferey
authors.affiliation: Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Canadian Blood Services, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada; Department of Physiology, University of Toronto, Toronto, ON, Canada.
authors.forename: Heyu
authors.initials: H
authors.lastname: Ni
authors.affiliation: Toronto Platelet Immunobiology Group, Toronto, ON, Canada; Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada; Canadian Blood Services, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada; Departments of Medicine and Pharmacology, University of Toronto, Toronto, ON, Canada. Electronic address: semplej@smh.ca.
authors.forename: John W
authors.initials: JW
authors.lastname: Semple
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000276:immunology*; D015415:Biomarkers; D001792:Blood Platelets / Q000276:immunology*; D001853:Bone Marrow / Q000473:pathology; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D039661:Integrin beta3 / Q000235:genetics / Q000276:immunology; D007958:Leukocyte Count; D008214:Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008533:Megakaryocytes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010641:Phenotype; D010976:Platelet Count; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology* / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D013154:Spleen / Q000276:immunology* / Q000473:pathology; D013156:Splenectomy; D050378:T-Lymphocytes, Regulatory / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D060168:Thymocytes / Q000276:immunology / Q000378:metabolism
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D015395:Histocompatibility Antigens Class I; D039661:Integrin beta3