Splenic changes related to TLR9-induced MAS are more pronounced in IL-18BP^−/−mice. Female WT and IL-18BP^−/− mice received CpG injections on days 0, 2, and 4 and were killed on day 7. (Ai) Spleen weights, normalized to body weight, of naive (control [ctrl]) and CpG-challenged WT (n = 8-11) and IL-18BP^−/− (n = 9-12) littermates (data pooled from 2 independent experiments) and (Aii) a representative photograph of the spleens of CpG-injected WT (left) and IL-18BP^−/− (right) mice are shown. (Bi) CD3 staining of spleen sections of 1 WT (left) and 1 IL-18BP^−/− (right) mouse before (upper panels, ctrl) and after (lower panels) CpG injections (original magnification ×20), representative of 2 independent experiments. The ratio between lymphoid follicles and spleen section area of naive (ctrl) and CpG-challenged WT (n = 6-10) and IL-18BP^−/− (n = 8-12) littermates is reported in panel Bii. Data were pooled from 2 independent experiments. The number of (Ci) total and CD45⁺ cells (n = 6-7), (Cii) total T cells, CD4⁺ T cells, CD8⁺ T cells and B cells (n = 10-11), and (Ciii) conventional DCs (cDCs), plasmacytoid DCs (pDCs), monocytes/macrophages (mono/macro), and neutrophils (neutro) (n = 10-11) in the spleen are shown for naive WT littermate and IL-18BP^−/− female mice (results were pooled from 2 independent experiments). The Mann-Whitney U test was used to compare WT and 18BP^−/− mice at 1 time point and to compare naive and CpG-challenged mice.