One study of immune responses of volunteers who had received the live attenuated monovalent dengue vaccines reported that restimulating memory CD4+ T cells in peripheral blood mononuclear cells with homologous inactivated dengue serotype resulted in the highest IFN-γ production whereas stimulation with heterologous serotypes resulted in the alteration of IFN-γ to TNF-alpha production [30]. Here, CD4 is linked to dengue disease.