CD40LG and infection: Igs have a basic structure with two antigen-binding sites and are initially produced as cell surface IgM, but upon antigen stimulation, the producing B cells start a process of affinity maturation, class switching and differentiation, which gives rise to antibody-secreting plasma cells, initially of IgM type but later as IgG, IgA or IgE type, depending on the stimulating antigens/microorganisms and the site of infection [1,24–28].