In fact, an altered response to polysaccharide vaccines, as well as an increased susceptibility to bacterial infections has been described in different groups of people with a reduced frequency of IgM memory B cells, e.g., newborns [30,31,42,46,47,91,92], congenitally asplenic and splenectomized individuals [29,46] or patients with common variable immunodeficiency [47,93]. Here, CD40LG is linked to common variable immunodeficiency.