CD40LG and viral infectious disease: It is possible the primary purpose of the initial polymorphic humoral response to viral infection – typically pentameric IgM – is to push viral replication towards equilibria favouring production of homogeneous virus, thus facilitating a concerted and more focussed humoral and/or cytotoxic T cell response; Strong neutralizing IgG antibodies – antiHBsAg, for example – may develop as a consequence of initially restricted viral replication and mutation permitting effective and specific immune recognition, rather than being the proximate cause of it.