<i>P</i>. <i>chabaudi</i>-specific IgG B-cell responses are abrogated in the absence of IL-21 signaling.

<p>(A) IgG, (B) IgG subtypes (day 32 post-infection) and (C) IgM antibodies specific for a lysate of <i>P</i>. <i>chabaudi</i>-infected rbc determined by ELISA. Antibody units (AU) were calculated based on the <i>P</i>. <i>chabaudi</i>-specific antibody levels of a hyper-immune standard plasma defined as 1000 U. In the cases where levels of antibodies were below background, arbitrary values of 2 log lower than the mean value observed in WT C57BL/6 mice were set to be able to perform the statistical test. (D) MSP1₂₁-specific IgG-producing ASC in BM obtained from one femur and one tibia, and (E) MBC per spleen, determined by ELISPOT 32 days post-infection. Statistical significance was obtained using the Kruskal-Wallis test comparing each time point with its respective basal level (day 0 post-infection) (*, P<0.05; **, P<0.01), or comparing with the data obtained from the WT C57BL/6 group (# #, P<0.01). The Mann Whitney U test was used in the case of IgG subtypes, comparing <i>Il21</i>^<i>-/-</i> vs WT C57BL/6 mice (#, P<0.05). Bars represent median values. Data are representative of at least two independent experiments and were obtained in groups of 3–8 mice per time point.