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Cellular immune responses to platelet factor 4 and heparin complexes in patients with heparin-induced thrombocytopenia. 2018

I Nazy, and R Clare, and P Staibano, and T E Warkentin, and M Larché, and J C Moore, and J W Smith, and R P Whitlock, and J G Kelton, and D M Arnold
Department of Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.

Essentials The immunogenesis of Heparin-induced thrombocytopenia (HIT) is not well understood. Immunization to platelet factor 4 (PF4)-heparin occurs early in life, before any heparin exposure. PF4 and PF4-heparin complexes induce the proliferation of CD14+ cells. Reduced levels of regulatory cytokines contribute to immune dysregulation in HIT. Background Heparin-induced thrombocytopenia (HIT) is an adverse reaction to heparin characterized by thrombocytopenia and thrombotic complications. HIT is caused by pathogenic antibodies that bind to complexes of platelet factor 4 (PF4) and heparin, leading to platelet activation and inducing a hypercoagulable state. Previous studies have shown immunity to PF4-heparin complexes occurs early in life, even before heparin exposure; however, the immunogenesis of HIT is not well characterized. Objectives To investigate cellular proliferation in response to PF4-heparin complexes in patients with HIT. Patients/Methods Peripheral blood mononuclear cells (PBMCs) from healthy controls (n = 30), postoperative cardiac surgery patients who had undergone cardiopulmonary bypass (CPB) (n = 17) and patients with confirmed HIT (n = 41) were cultured with PF4 and PF4-heparin complexes. Cellular proliferation was assessed by [3 H]thymidine uptake and 5-ethynyl-2'-deoxyuridine detection. Results and Conclusions PBMCs proliferated in the presence of PF4, and this was enhanced by the addition of heparin in all study groups. CPB and HIT patients showed significantly greater proliferative responses than healthy controls. PBMC proliferation was antigen-specific, depended on the presence of platelets, and only CD14+ cells were identified as proliferating cells. Culture supernatants were tested for the levels of regulatory cytokines, and both CPB and HIT patients produced significantly lower levels of interleukin-10 and transforming growth factor-β1 than healthy controls. These findings further demonstrate cellular immune sensitization to PF4-heparin complexes occurs before heparin exposure, and suggests immune dysregulation can contribute to HIT.

UI MeSH Term Description Entries
D007111 Immunity, Cellular Manifestations of the immune response which are mediated by antigen-sensitized T-lymphocytes via lymphokines or direct cytotoxicity. This takes place in the absence of circulating antibody or where antibody plays a subordinate role. Cell-Mediated Immunity,Cellular Immune Response,Cell Mediated Immunity,Cell-Mediated Immunities,Cellular Immune Responses,Cellular Immunities,Cellular Immunity,Immune Response, Cellular,Immune Responses, Cellular,Immunities, Cell-Mediated,Immunities, Cellular,Immunity, Cell-Mediated,Response, Cellular Immune
D007963 Leukocytes, Mononuclear Mature LYMPHOCYTES and MONOCYTES transported by the blood to the body's extravascular space. They are morphologically distinguishable from mature granulocytic leukocytes by their large, non-lobed nuclei and lack of coarse, heavily stained cytoplasmic granules. Mononuclear Leukocyte,Mononuclear Leukocytes,PBMC Peripheral Blood Mononuclear Cells,Peripheral Blood Human Mononuclear Cells,Peripheral Blood Mononuclear Cell,Peripheral Blood Mononuclear Cells,Leukocyte, Mononuclear
D008297 Male Males
D008875 Middle Aged An adult aged 45 - 64 years. Middle Age
D010978 Platelet Factor 4 A CXC chemokine that is found in the alpha granules of PLATELETS. The protein has a molecular size of 7800 kDa and can occur as a monomer, a dimer or a tetramer depending upon its concentration in solution. Platelet factor 4 has a high affinity for HEPARIN and is often found complexed with GLYCOPROTEINS such as PROTEIN C. Antiheparin Factor,CXCL4 Chemokine,Chemokine CXCL4,Heparin Neutralizing Protein,PF4 (Platelet Factor 4),gamma-Thromboglobulin,CXCL4, Chemokine,Chemokine, CXCL4,gamma Thromboglobulin
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D005260 Female Females
D006493 Heparin A highly acidic mucopolysaccharide formed of equal parts of sulfated D-glucosamine and D-glucuronic acid with sulfaminic bridges. The molecular weight ranges from six to twenty thousand. Heparin occurs in and is obtained from liver, lung, mast cells, etc., of vertebrates. Its function is unknown, but it is used to prevent blood clotting in vivo and vitro, in the form of many different salts. Heparinic Acid,alpha-Heparin,Heparin Sodium,Liquaemin,Sodium Heparin,Unfractionated Heparin,Heparin, Sodium,Heparin, Unfractionated,alpha Heparin
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults

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