Altered immune cell differentiation in the lungs of patients with critical COVID-19

This preprint from Wauters et al. analysed the single-cell transcriptome of bronchoalveolar lavages from 5 patients with mild and 26 patients with critical COVID-19, and detected important differences in immune cell functionality. In mild COVID-19, T cells assumed a resident memory CD8⁺ or T helper 17 (T_H17) cell phenotype, whereas in critical COVID-19 they acquired an exhausted phenotype. In mild COVID-19, monocytes differentiated into macrophages with phagocytic and antigen-presenting capacity, whereas in critical COVID-19 monocytes did not differentiate and showed a pro-inflammatory phenotype. Interestingly, neutrophils showed a large capacity to phagocytose viral particles and/or infected cells. Future longitudinal analyses may show how immune cell differentiation correlates to the disease course of COVID-19.