CD27 and COVID-19: To investigate whether SARS-CoV-2 infection affects the B-cell immune phenotype, we first examined the naive B cells (CD27−IgD+), atypical (CD27−IgD−), switched (CD27+IgD−) and unswitched (CD27+IgD+) memory B cells, transitional B cells (CD38+CD24hi), and plasma blast cells (PBC, CD38+CD24−) in PBMCs from recovered COVID-19 patients and healthy controls.