The same authors suggested that the early parallel production of IgM and IgG in response to SARS-CoV-2 infection might be mediated by the stimulation of IgG memory B cells, as well as by naïve B cells (59) indicating that the memory generated by previous infections with other HCoVs would trigger a response to infection by the current SARS-CoV-2. This evidence concerns the gene CD40LG and infection.