Moreover, as predicted, the number of IL-21-producing CD4+ T cells detected at the peak of infection in Bcl6fl/flCD4-cre+/− mice was reduced to approximately half the amount of these cells in wt controls, thus showing that the Tfh response represents an important, but not the only, source of IL-21 during P. chabaudi infection (Fig. 10). Here, IL21 is linked to infection.