Characterization of T cell, B cell and Natural Killer Cell Subsets in COVID-19 Patients

Abstract

Immune dysregulation is observed in patients with severe COVID-19 associated pneumonia. The aim of the investigation was to perform analysis of immune parameters including cell count, differentiation and activation of lymphocytes from COVID-19 patients. 57 patients with PCR and chest CT confirmed diagnosis of COVID-19 pneumonia were included in the study. Patients were divided into 2 groups: severe/critical (S/C) patients (n=18) which were treated in ICU and required IMV; and moderate (M) patients (n=39). Blood samples from 19 healthy donors (HD) controls were obtained. T cell, B cell, natural killer (NK) cell and innate lymphoid cell (ILC) subsets were assayed using Attune NxT flow cytometer. Nonparametric statistics were used. A profound decrease of the absolute counts of T-cells, B-cells, NK- and NKT-cells and frequencies (%) of ILC was noted both in S/C and M versus HD (p<0.01). Frequency (%) of B-cells in S/C was increased. A decrease in the content of naive T-cells was noted, while the content of TCM, TEM, TEMRA, T-reg and activated HLA-DR+ T-cells did not change significantly in S/C compared with M but both groups had increased exhausted PD-1+ T cells counts. T and NK cell lymphopenia was observed in COVID-19 patients, more significant in S/C. No important changes in T-cells differentiation and activation were detected in with S/C or M groups accompanied by increase in exhausted T cells. Immune system anergy may explain the severe course of some COVID 19 patients and cases of reinfection.