Immune memory is a key factor in the protection from recurring infections and, among their diverse compartments, memory B cell subsets expressing IgM are particularly interesting due to their role against specific pathogens, such as encapsulated bacteria, and also as a source of long-lived memory, as switched memory B cells [28,29,30,31,32,33,34,35,36,37]. This evidence concerns the gene CD40LG and infection.