Suppressive Monocytes Impair MAIT Cells Response via IL-10 in Patients with Severe COVID-19

Area of Science:

• Immunology
• Virology
• Cell Biology

Background:

• Immune cell alterations are observed in severe COVID-19, but the underlying immunoregulatory mechanisms remain unclear.
• Understanding these changes is crucial for developing targeted therapies for severe coronavirus disease 2019.

Purpose of the Study:

• To comprehensively profile peripheral immune cells in patients with varying COVID-19 severity.
• To elucidate the immunoregulatory processes contributing to severe COVID-19 pathogenesis.
• To identify potential therapeutic targets for restoring immune function.

Main Methods:

• Mass cytometry was used to profile peripheral immune cells from healthy controls and patients with mild, severe COVID-19, and asymptomatic carriers.
• Single-cell transcriptome analysis was performed to investigate gene expression patterns in immune cells.
• Functional assays were conducted to assess MAIT cell responses and the impact of cytokine signaling.

Main Results:

• Severe COVID-19 is characterized by increased HLA-DRlow/- monocytes and reduced mucosal-associated invariant T (MAIT) cells.
• MAIT cells in severe COVID-19 patients show activation but functional impairment, particularly with coinfection.
• IFN-α and IL-10 signaling, mediated by suppressive monocytes, were identified as key pathways inhibiting MAIT cell function, with plasma from severe COVID-19 patients exacerbating this effect.

Conclusions:

• Severe COVID-19 exhibits unique immune dysregulation involving suppressive monocytes and functionally impaired MAIT cells.
• The IFN/IL-10 pathway, driven by HLA-DRlow/- monocytes, plays a critical role in MAIT cell dysfunction.
• Targeting the IFN-α/IL-10 pathway presents a potential therapeutic strategy for severe COVID-19.