CD40LG and infection: Considering that the antibody, which was developed from a monotypic immune response, could protect individuals from re-infection by the homologous serotype [5], the scenario of IgM-/IgG+ in patients during the acute infection phase implied that the patients had been infected by the homologous serotype virus, which stimulated a pre-existing subset of plasma cells or memory B cells to produce anti-DENV IgG antibodies against the virus.