To further assess the consequences of Tfh deficiency on P. yoelii XNL compared with P. chabaudi AS malaria infection, we infected IL-21R-/- mice which can generate comparable levels of Tfh cells and germinal center responses during the early stages of an LCMV infection (around 15 days), but fail to maintain both Tfh and germinal center responses after 2 weeks of infection [30], recapitulating the immunological phenotype of MHV68 and malaria co-infected animals. The gene discussed is IL21R; the disease is malaria.