SELL and COVID-19: Last, to assess the possible relevance of the CD62L+ Bmem cell subset on disease severity, we longitudinally tracked the development and persistence of the CD62L+ and CD62L− subsets in the RBD-binding IgG+CD21+CD27+ memory compartment in COVID-19–convalescent individuals who had recovered from mild or moderate diseases (mild, 16 donors; moderate, 20 donors; fig.