title: Pneumolysin mediates heterotypic aggregation of neutrophils and platelets in vitro.
abstract: Platelets orchestrate the inflammatory activities of neutrophils, possibly contributing to pulmonary and myocardial damage during severe pneumococcal infection. This study tested the hypothesis that the pneumococcal toxin, pneumolysin (Ply), activates production of platelet-activating factor (PAF) and thromboxane A2(TxA2) by neutrophils, these bioactive lipids being potential mediators of neutrophil:platelet (NP) networking.
  
  
  
  The effects of recombinant Ply (10-80 ng mL-1) on the production of PAF and TxA2by isolated neutrophils were measured using ELISA procedures, and NP aggregation by flow cytometry.
  
  
  
  Exposure of neutrophils to Ply induced production of PAF and, to a lesser extent, TxA2, achieving statistical significance at ≥20 ng mL-1of the toxin. In the case of NP interactions, Ply promoted heterotypic aggregation which was dependent on upregulation of P-selectin (CD62P) and activation of protease-activated receptor 1 (PAR1), attaining statistical significance at ≥10 ng mL-1of the toxin, but did not involve either PAF or TxA2.
  
  
  
  Ply induces synthesis of PAF and TxA2,by human neutrophils, neither of which appears to contribute to the formation of NP heterotypic aggregates in vitro, a process which is seemingly dependent on CD62P and PAR1. These pro-inflammatory activities of Ply may contribute to the pathogenesis of pulmonary and myocardial injury during severe pneumococcal infection.
authors.affiliation: Department of Haematology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa; Tshwane Academic Division of the National Health Laboratory Service, Pretoria, South Africa. Electronic address: jan.nel@up.ac.za.
authors.forename: Jan G
authors.initials: JG
authors.lastname: Nel
authors.affiliation: Institute for Cellular and Molecular Medicine, South African Medical Research Council Unit for Stem Cell Research, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Chrisna
authors.initials: C
authors.lastname: Durandt
authors.affiliation: Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Annette J
authors.initials: AJ
authors.lastname: Theron
authors.affiliation: Department of Internal Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Tintinger
authors.affiliation: Department of Haematology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa; Tshwane Academic Division of the National Health Laboratory Service, Pretoria, South Africa.
authors.forename: Roger
authors.initials: R
authors.lastname: Pool
authors.affiliation: Department of Critical Care, Charlotte Maxeke Johannesburg Academic Hospital, Johannesburg, South Africa; Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Guy A
authors.initials: GA
authors.lastname: Richards
authors.affiliation: Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mitchell
authors.affiliation: Division of Pulmonology, Department of Internal Medicine, Charlotte Maxeke Johannesburg Academic Hospital, Johannesburg, South Africa.
authors.forename: Charles
authors.initials: C
authors.lastname: Feldman
authors.affiliation: Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa; Institute for Cellular and Molecular Medicine, South African Medical Research Council Unit for Stem Cell Research, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Ronald
authors.initials: R
authors.lastname: Anderson
mesh_terms: D001426:Bacterial Proteins / Q000494:pharmacology / Q000502:physiology; D001792:Blood Platelets / Q000502:physiology*; D002352:Carrier Proteins / Q000096:biosynthesis; D002449:Cell Aggregation; D002470:Cell Survival; D004268:DNA-Binding Proteins; D006801:Humans; D018375:Neutrophil Activation; D009504:Neutrophils / Q000502:physiology*; D019007:P-Selectin / Q000235:genetics; D015539:Platelet Activation; D010974:Platelet Aggregation; D011994:Recombinant Proteins / Q000494:pharmacology; D013296:Streptococcus pneumoniae / Q000737:chemistry; D013301:Streptolysins / Q000494:pharmacology* / Q000502:physiology*; D013928:Thromboxane A2 / Q000096:biosynthesis
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D019007:P-Selectin; C425208:PCLAF protein, human; D011994:Recombinant Proteins; C546937:SELP protein, human; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae; D013928:Thromboxane A2
keywords: Calcium; P-selectin (CD62P); Platelet-activating factor; Pneumolysin; Severe pneumococcal disease