CD40LG and COVID-19: A recent study on convalescent COVID-19 individuals showed that there was a good correlation between the SARS-CoV-2 pseudovirus-neutralizing activity of IgG and IgA in plasma in a given individual, and clones of IgM-, IgG-, and IgA-producing B cells were found to be derived from common progenitor cells (Wang et al., 2021).