Studies using the mixed bone marrow chimeric mice also indicated that T-cell-derived (i.e., TFH cells) IL-21 interacted with the IL-21R expressed on B cells for the effective control of parasitemia during P. chabaudi infection, highlighting the requirement of T-cell/B cell crosstalk for the development and the maintenance of a robust and protective anti-malaria immune response in the mouse (Perez-Mazliah et al., 2015). This evidence concerns the gene IL21 and parasitic infectious disease.