CD40LG and COVID-19: The study by Newell KL et al revealed that in convalescent COVID-19 patients, the presence of memory B cells in the peripheral blood exhibited an inverse correlation with the duration of symptoms.[43] These memory B cells encompassed various subsets, including classical CD24 + class-switched, activated CD24-negative, and natural unswitched CD27 + IgD + IgM + subsets.