Fig. 1

SARS-CoV-2 infection alters the immune phenotype and function of B cells and reduces CD19 expression on B cells from recovered COVID-19 patients. Flow cytometry analysis of the frequencies of naive B cells (naive, CD19⁺ IgD⁺CD27⁻), class-switched B cells (switched, CD19⁺ IgD⁻CD27⁺), unswitched memory B cells (unswitched, CD19⁺IgD⁺CD27⁺), transitional B cells (transitional, CD19⁺CD24⁺CD38⁺), plasma blasts (PBC, CD19⁺CD38⁺CD24⁻) and atypical memory B cells (atypical, CD19⁺IgD⁻CD27⁻) in resting and stimulated PBMCs from COVID-19 recovered patients (n = 14–15) and healthy controls (n = 15). Shown are representative dot plots (a, d) and the average percentages (±SEM) of B-cell subpopulations (b, c, e). Flow cytometry analysis of the MFI of CD19 on total B cells (B, CD19⁺), naive B cells, class-switched B cells, unswitched memory B cells, transitional B cells, plasma blasts, and atypical memory B cells in resting PBMCs from COVID-19 recovered patients (n = 15) and healthy controls (n = 15). Resting = cells before stimulation, Stimulated = cells after stimulation with 10 µg/ml biotin-F(ab′)₂-anti-Ig(M + G) for 24 h (f). RT-PCR analysis of CD19 mRNA levels of B cells from recovered patients (n = 4) and healthy controls (n = 4) (g). Immunofluorescence analysis of CD19 expression in nephritic sections from SARS-CoV-2 infected mice (n = 3) and mock mice (n = 3). Shown are representative images (h, i). Statistical evaluation was performed using the two-tailed Student’s t-test. Statistical significance is indicated using asterisks: *p < 0.05,**p < 0.01, ***p < 0.001, and ****p < 0.0001