title: Essential roles for platelets during neutrophil-dependent or lymphocyte-mediated defense against bacterial pathogens.
abstract: Emerging evidence from animal models suggests that platelets may participate in a wide variety of processes including the immune response against infection. More than 200 whole blood samples from patients and healthy controls were run in the System XE-5000 analyzer, and plasma fractions were separated for the following tests by ELISA, Luminex and light scattering. We describe two mechanisms by which platelets may contribute to immune function against various bacterial pathogens based on increased mean platelet volume in gram-positive bacterial infections and increased platelet counts in gram-negative bacterial infections. Gram-negative bacteria activate platelets to recruit neutrophils, which participate in the immune response against infection. During this process, fractalkine, macrophage inflammatory protein-1β, interleukin-17A, tumor necrosis factor-α and platelet-activating factor were higher in patients infected with Escherichia coli; additionally, giant platelets were observed under the microscope. Meanwhile, we found that platelets played a different role in gram-positive bacterial infections. Specifically, they could actively adhere to gram-positive bacteria in circulation and transfer them to immune sites to promote antibacterial lymphocyte expansion. During this process, complement C3 and factor XI were more highly expressed in patients infected with Staphylococcus aureus; additionally, we detected more small platelets under the microscope. Platelets participate in the immune response against both gram-negative and gram-positive bacteria, although the mechanisms differ. These results will help us understand the complex roles of platelets during infections, and direct our use of antibiotics based on clinical platelet data.
authors.affiliation: aDepartment of Pediatric Surgery, General Hospital of PLA, Beijing bYuhuangding Hospital, Yantai cDepartment of Immunology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China *Dr Zheng Wang and Dr Qi Zhao contributed equally to the writing of this article.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhao
authors.forename: Dongxia
authors.initials: D
authors.lastname: Zhang
authors.forename: Chengming
authors.initials: C
authors.lastname: Sun
authors.forename: Cuixia
authors.initials: C
authors.lastname: Bao
authors.forename: Maoli
authors.initials: M
authors.lastname: Yi
authors.forename: Li
authors.initials: L
authors.lastname: Xing
authors.forename: Deyan
authors.initials: D
authors.lastname: Luo
mesh_terms: D000293:Adolescent; D000328:Adult; D001792:Blood Platelets / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D054407:Chemokine CCL4 / Q000235:genetics / Q000276:immunology; D054428:Chemokine CX3CL1 / Q000235:genetics / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D003176:Complement C3 / Q000235:genetics / Q000276:immunology; D004926:Escherichia coli / Q000276:immunology; D004927:Escherichia coli Infections / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D005172:Factor XI / Q000235:genetics / Q000276:immunology; D005260:Female; D015870:Gene Expression; D006801:Humans; D007113:Immunity, Innate; D020381:Interleukin-17 / Q000235:genetics / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D008297:Male; D063847:Mean Platelet Volume; D008875:Middle Aged; D009504:Neutrophils / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D015539:Platelet Activation; D010973:Platelet Adhesiveness; D010976:Platelet Count; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D013211:Staphylococcus aureus / Q000276:immunology
chemical_list: C515538:CX3CL1 protein, human; D054407:Chemokine CCL4; D054428:Chemokine CX3CL1; D003176:Complement C3; C508717:IL17A protein, human; D020381:Interleukin-17; D005172:Factor XI