Several recent findings have shown that CD8+ T cells are capable of secreting IL-10 with or without CD4+ T-cell help and are involved in the regulation of immune response during virus or parasite infection (Bourreau et al., 2007; Sun et al., 2011; Trandem et al., 2011; Buxbaum, 2015; Jiang et al., 2016). Here, CD4 is linked to parasitic infectious disease.