CD27 and systemic lupus erythematosus: The re-emerged B cells had a different immunophenotype than those before CAR-T-cell infusion, being primarily CD21 + CD27– naïve cells, with low numbers (or absent) of CD21 + CD27+ memory B cells, CD38 + CD20− plasmablasts, and CD11c + CD21lo activated memory B cells, which are typically expanded in SLE.