Disruption of IL-21 Signaling Affects T Cell-B Cell Interactions and Abrogates Protective Humoral Immunity to Malaria
Fig 5
IL-21-producing Tfh cells are activated during acute P. chabaudi infection.
(A) Flow cytometric analysis of representative naïve (top row) and infected mice (8 days post-infection, bottom row). Gates show frequency of CD3+CD4+CD44high cells expressing CXCR5 and PD-1. (B) Frequency and (C) total numbers of Tfh cells, defined as CD3+CD4+CD44highCXCR5+PD-1+, in WT C57BL/6, Il21-/-, Il21r-/- and Ighm mice. (D) Flow cytometric analysis representative of infected WT C57BL/6 mice (8 days post-infection) corresponding to IL-21 intracellular staining on CD4+ T cells (red), overlaid on side scatter light vs CD44 (left) and CXCR5 vs PD-1 (right) from CD3+CD4+ T cells. Numbers show frequency of IL-21-producing CD4+ T cells with high expression of CD44 (left), and their differential expression of CXCR5 and PD-1 (right). (E) Differential combination of expression (+) or absence of expression (–) of CD44, CXCR5 and PD-1 (bottom left) on IL-21-producing CD3+CD4+ T cells at different days post-infection in the spleen of WT C57BL/6 mice. (F) Flow cytometric analysis of IFN-γ (green line) on CD3+CD4+CD44highCXCR5+PD-1+IL-21+ T cells from the spleen of WT C57BL/6 mice, 8 days post-P. chabaudi infection (representative of 4 mice). (G) Serum IL-6 at day 6 post-P. chabaudi 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; ***, P<0.001), or comparing with the data obtained from the WT C57BL/6 group (#, P<0.05; # #, P<0.01). Bars represent median values. Data are representative of at least two independent experiments and were obtained in groups of 4–7 mice per time point.