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J Extracell Vesicles ; 10(14): e12173, 2021 12.
Article in English | MEDLINE | ID: covidwho-1544291


Infection with SARS-CoV-2 is associated with thromboinflammation, involving thrombotic and inflammatory responses, in many COVID-19 patients. In addition, immune dysfunction occurs in patients characterised by T cell exhaustion and severe lymphopenia. We investigated the distribution of phosphatidylserine (PS), a marker of dying cells, activated platelets and platelet-derived microparticles (PMP), during the clinical course of COVID-19. We found an unexpectedly high amount of blood cells loaded with PS+ PMPs for weeks after the initial COVID-19 diagnosis. Elevated frequencies of PS+ PMP+ PBMCs correlated strongly with increasing disease severity. As a marker, PS outperformed established laboratory markers for inflammation, leucocyte composition and coagulation, currently used for COVID-19 clinical scoring. PS+ PMPs preferentially bound to CD8+ T cells with gene expression signatures of proliferating effector rather than memory T cells. As PS+ PMPs carried programmed death-ligand 1 (PD-L1), they may affect T cell expansion or function. Our data provide a novel marker for disease severity and show that PS, which can trigger the blood coagulation cascade, the complement system, and inflammation, resides on activated immune cells. Therefore, PS may serve as a beacon to attract thromboinflammatory processes towards lymphocytes and cause immune dysfunction in COVID-19.

COVID-19/blood , Leukocytes, Mononuclear/metabolism , Phosphatidylserines/blood , Adult , Blood Platelets/immunology , CD8-Positive T-Lymphocytes/immunology , COVID-19/immunology , COVID-19/physiopathology , Cell-Derived Microparticles/metabolism , Flow Cytometry , Humans , Platelet Membrane Glycoprotein IIb , Severity of Illness Index , Transcriptome
PLoS Pathog ; 17(10): e1009742, 2021 10.
Article in English | MEDLINE | ID: covidwho-1456098


Disease manifestations in COVID-19 range from mild to severe illness associated with a dysregulated innate immune response. Alterations in function and regeneration of dendritic cells (DCs) and monocytes may contribute to immunopathology and influence adaptive immune responses in COVID-19 patients. We analyzed circulating DC and monocyte subsets in 65 hospitalized COVID-19 patients with mild/moderate or severe disease from acute illness to recovery and in healthy controls. Persisting reduction of all DC subpopulations was accompanied by an expansion of proliferating Lineage-HLADR+ cells lacking DC markers. Increased frequency of CD163+ CD14+ cells within the recently discovered DC3 subpopulation in patients with more severe disease was associated with systemic inflammation, activated T follicular helper cells, and antibody-secreting cells. Persistent downregulation of CD86 and upregulation of programmed death-ligand 1 (PD-L1) in conventional DCs (cDC2 and DC3) and classical monocytes associated with a reduced capacity to stimulate naïve CD4+ T cells correlated with disease severity. Long-lasting depletion and functional impairment of DCs and monocytes may have consequences for susceptibility to secondary infections and therapy of COVID-19 patients.

COVID-19/immunology , Dendritic Cells/immunology , Regeneration/immunology , SARS-CoV-2/immunology , Adult , Antigens, CD/immunology , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/pathology , COVID-19/pathology , Dendritic Cells/pathology , Female , Humans , Male , Middle Aged , Monocytes/immunology , Monocytes/pathology , Programmed Cell Death 1 Receptor/immunology