The assembly of neutrophil inflammasomes during COVID-19 is mediated by type I interferons.

The severity of COVID-19 is linked to excessive inflammation. Neutrophils represent a critical arm of the innate immune response and are major mediators of inflammation, but their role in COVID-19 pathophysiology remains poorly understood. We conducted transcriptomic profiling of neutrophils obtained from patients with mild and severe COVID-19, as well as from SARS-CoV-2 infected mice, in comparison to non-infected healthy controls.

Maturing neutrophils of lower density associate with thrombocytopenia in Puumala orthohantavirus-caused hemorrhagic fever with renal syndrome.

Puumala orthohantavirus-caused hemorrhagic fever with renal syndrome (PUUV-HFRS) is characterized by strong neutrophil activation. Neutrophils are the most abundant immune cell type in the circulation and are specially equipped to rapidly respond to infections. They are more heterogenous than previously appreciated, with specific neutrophil subsets recently implicated in inflammation and immunosuppression.

Increased type 1 inflammation in gynecologic cervicovaginal samples in patients with APS-1.

Background: Inborn errors of immunity offer important insights into mucosal immunity. In autoimmune polyendocrine syndrome type-1 (APS-1), chronic mucocutaneous candidiasis has been ascribed to neutralizing IL-17 autoantibodies. Recent evidence implicates excessive T-cell IFN-γ secretion and ensuing epithelial barrier disruption in predisposition to candidiasis, but these results remain to be replicated.

Stable Levels of Antibodies Against Unrelated Toxoid Vaccines After COVID-19: COVID-19 Infection Does Not Affect Toxoid Vaccine Antibody Levels.

Background: Lymphopenia is common in COVID-19. This has raised concerns that COVID-19 could affect the immune system akin to measles infection, which causes immune amnesia and a reduction in protective antibodies.

Methods: We recruited COVID-19 patients (n = 59) in Helsinki, Finland, and collected plasma samples on 2 to 3 occasions during and after infection.

Mucosal-Associated Invariant T Cells are not susceptible in vitro to SARS-CoV-2 infection but accumulate into the lungs of COVID-19 patients.

Prolonged T cell lymphopenia is common in COVID-19, caused by SARS-CoV-2. While the mechanisms of lymphopenia during COVID-19 remain elusive, it is especially pronounced in a specialized innate-like T cell population called Mucosal Associated Invariant T cells (MAITs). MAITs has been suggested to express Angiotensin-Converting Enzyme 2 (ACE2), which is the well-known cellular receptor for SARS-CoV-2.

Characterization of low-density granulocytes in COVID-19.

Severe COVID-19 is characterized by extensive pulmonary complications, to which host immune responses are believed to play a role. As the major arm of innate immunity, neutrophils are one of the first cells recruited to the site of infection where their excessive activation can contribute to lung pathology. Low-density granulocytes (LDGs) are circulating neutrophils, whose numbers increase in some autoimmune diseases and cancer, but are poorly characterized in acute viral infections.

Real-life clinical sensitivity of SARS-CoV-2 RT-PCR test in symptomatic patients.

Background: Understanding the false negative rates of SARS-CoV-2 RT-PCR testing is pivotal for the management of the COVID-19 pandemic and it has implications for patient management. Our aim was to determine the real-life clinical sensitivity of SARS-CoV-2 RT-PCR.

Methods: This population-based retrospective study was conducted in March-April 2020 in the Helsinki Capital Region, Finland.