Ueland T, Heggelund L, Lind A, et al. - Researchers analyzed parameters of activation of different leukocyte subsets in relation to disease severity among patients infected with COVID-19. This study involved 39 COVID-19 infected patients. Experts found that there was a link between severe clinical outcome (ICU) and high plasma concentrations soluble T cell immunoglobulin mucin domain-3 (sTIM-3) and myeloperoxidase (MPO) indicating activated and potentially exhausted T cells and activated neutrophils, respectively. They found sCD14 and sCD163 were not related to requirement for ICU treatment. An inverse correlation of sCD25, sTIM-3 and MPO, with the degree of respiratory failure, as evaluated by P/F ratio (arterial partial pressure of oxygen to fraction of inspired oxygen), as well as a positive correlation with the cardiac marker N-terminal pro-B-type natriuretic peptide, was also identified. Overall, experts inferred a likely crucial role of neutrophil activation, and in particular activated T cells, in the pathogenesis of COVID-19 infection. This indicates the possible importance of T cell targeted treatment choices and downregulation of neutrophil activation in this disease.