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. 2026 Jan 23;16:1724684. doi: 10.3389/fimmu.2025.1724684

Figure 1.

Figure displaying data related to CFU (colony-forming units) in tissue, infected myeloid cells, and osteoclasts (OC) among different mouse models. A shows a bar graph comparing CFU per gram of tissue in liver, spleen, and bone marrow between MyD88-/- and control mice. B features fluorescent images illustrating CD68 and Coxiella in tissue sections of different mouse models at 5 and 14 days post-infection. C presents a bar chart of infected CD68+ myeloid cells per square millimeter. D displays images showing TRAP and Coxiella in tissue sections. E and F provide bar graphs of infected OC as percentages of total OC and infected cells.

C. burnetii can infect bone marrow myeloid cells including osteoclasts in vivo. (A)C. burnetii was injected intraperitoneally (i.p.) in control (ctrl) or Myd88 knock out mice (1.0 × 107 b/mice). The number of living C. burnetii in liver, spleen and bone marrow (CFU) of these mice was measured by limiting dilution (n = 10 for ctrl; n=9 for knock out mice). (B) Control (ctrl), Myd88-/- or Rag2-/- γ-Chain-/- mice were similarly infected i.p. for 5 or 14 days. The localization of C. burnetii in myeloid cells of the BM was analyzed in the femurs of these mice (n = 6 for ctrl and Myd88-/- mice; n=3 for Rag2-/- γ-Chain-/- mice). Bone tissues were cryosectioned and stained for Coxiella (green-Alexa488), CD68 (expressed by osteoclasts and macrophages; red-Alexa555), and DNA (blue-DAPI). Sections were imaged by CLSFM. Foci of infection are marked with white arrows. Inserts of infected CD68 expressing cells lining a trabecula are depicted within dashed line. Scale bar represents 100 µm. (C) Number of infected CD68+ myeloid cells per mm2 of bone marrow section was quantified (n=3 to 4 mice for each condition). (D) The co-localization of C. burnetii with osteoclast was analyzed in the femurs of ctrl and Myd88-/- infected mice. Bone tissues were cryosectioned and stained for Coxiella (green-Alexa594) and TRAP (expressed by osteoclasts only; blue-ELF97). Sections were imaged by CLSFM. Foci of infection are marked with white arrows. Inserts of infected osteoclast are depicted within dashed line. Scale bar represents 50 µm. (E) Percentage of infected osteoclast among all osteoclast was quantified (n=3 mice for each condition). (F) Percentage of osteoclasts among all infected cells of the BM was quantified (n=3 mice for each condition). Data are shown as mean ± SD.