Increased B-cell activity with consumption of activated monocytes in severe COVID-19 patients

Eur J Immunol. 2021 Jun;51(6):1449-1460. doi: 10.1002/eji.202049163. Epub 2021 Apr 19.


The pathogenesis of autoimmune complications triggered by SARS-CoV2 has not been completely elucidated. Here, we performed an analysis of the cellular immune status, cell ratios, and monocyte populations of patients with COVID-19 treated in the intensive care unit (ICU) (cohort 1, N = 23) and normal care unit (NCU) (cohort 2, n = 10) compared with control groups: patients treated in ICU for noninfectious reasons (cohort 3, n = 30) and patients treated in NCU for infections other than COVID-19 (cohort 4, n = 21). Patients in cohort 1 presented significant differences in comparison with the other cohorts, including reduced frequencies of lymphocytes, reduced CD8+T-cell count, reduced percentage of activated and intermediate monocytes and an increased B/T8 cell ratio. Over time, patients in cohort 1 who died presented with lower counts of B, T, CD4+ T, CD8+ T-lymphocytes, NK cells, and activated monocytes. The B/T8 ratio was significantly lower in the group of survivors. In cohort 1, significantly higher levels of IgG1 and IgG3 were found, whereas cohort 3 presented higher levels of IgG3 compared to controls. Among many immune changes, an elevated B/T8-cell ratio and a reduced rate of activated monocytes were mainly observed in patients with severe COVID-19. Both parameters were associated with death in cohort 1.

Keywords: Autoimmunity ⋅ B/T-cell ratio ⋅ COVID-19 ⋅ Lymphocytes ⋅ Monocytes.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Antibodies, Viral / immunology
  • B-Lymphocytes / immunology*
  • B-Lymphocytes / pathology
  • CD4-Positive T-Lymphocytes / immunology
  • CD4-Positive T-Lymphocytes / pathology
  • CD8-Positive T-Lymphocytes / immunology
  • CD8-Positive T-Lymphocytes / pathology
  • COVID-19 / immunology*
  • COVID-19 / pathology
  • Female
  • Humans
  • Immunoglobulin G / immunology
  • Lymphocyte Count
  • Male
  • Middle Aged
  • Monocytes / immunology*
  • Monocytes / pathology
  • Prospective Studies
  • SARS-CoV-2 / immunology*
  • Severity of Illness Index


  • Antibodies, Viral
  • Immunoglobulin G