Fig 1: Co-infection limits pathogenic CD4 + T-cell and pro-inflammatory immune-cell infiltration into the joints. a Representative IHC images of CD3 staining in the joints at 6 dpi. Scale bar: 100 µm. Quantification of CD3 + cells (IHC) (b), CD3 + cells (flow cytometry) (c), activated (LFA-1 + ) CD4 + T cells (flow cytometry) (d) and CHIKV-specific CD4 + T cells (ELISPOT) (e) in the joints of CHIKV, CHIKV + PbA and Py17x (-4 dpi) + CHIKV (n = 5 per group) at 6 dpi. Flow cytometric quantification of neutrophils (f), NK cells (g) and CD11b + Ly6C + monocytes (h) in the joints of CHIKV, CHIKV + PbA and Py17x (-4 dpi) + CHIKV (n = 5 per group) at 6 dpi. Data represent the means ± SD and were analyzed by one-way ANOVA with Tukey post hoc test (*P < 0.05, **P < 0.01 and ***P < 0.001). Each data point in the dot plot represents one mouse. Data are representative of two independent experiments. Activated CD4 + T cells are defined as CD45 + /CD3 + CD4 + /LFA-1 + cells. Neutrophils and NK cells are defined as CD45 + /CD11b + /Ly6G + and CD45 + /NK1.1 + cells, respectively. CD11b + /Ly6C + monocytes were gated after gating out all T cells, neutrophils, NK cells and B cells. Abbreviations: CHIKV, Chikungunya virus; dpi, days post infection; IHC, immunohistochemistry; NK, natural killer; ns, not significant; PbA, Plasmodium berghei-ANKA