Figure 3.

CD4 T cells homing to the choroid plexus (CP) locally impact antigen-presenting cell subsets. Activated CD45.1⁺ Th1 cells were intracerebroventricularly (ICV)-injected into the lateral ventricles (LVs) of either untreated (UT) or lipopolysaccharide (LPS)-preconditioned (+LPS) CD45.2 wild-type mice. The LV CPs of these mice were then analyzed with flow cytometry, either 1 days post-injection (dpi) (A–C) or 3 dpi (A–C,E–H), and with immunohistochemistry (IHC) 3 dpi (D). Flow cytometry analyses of gated CD45.2⁺CD11b⁺ mononuclear myeloid cells of LV CPs isolated from UT mice (n = 10) or from mice that had been ICV-injected with Th1 cells, either with (1 dpi, n = 7; 3 dpi, n = 5) or without (1 dpi, n = 8; 3 dpi, n = 7) LPS preconditioning. (A,B) The frequency of CD45.2⁺CD11b⁺ mononuclear myeloid cells in individual mice (A) and their expression levels of intercellular adhesion molecule 1 (ICAM-1) (B). (C) The frequency of CD11c subsets among the myeloid population. (D) Representative IHC images, showing the LV CPs of mice that were preconditioned with LPS and ICV-injected with Th1 cells. Images were taken 3 dpi and immunolabeled with anti-ICAM-1 (green), anti-Ki-67 (red), anti-MHC II (blue), and a DAPI nuclear counterstain (gray). Scale bars: 200 µm (top left), 50 µm (bottom left), and 10 µm (top right). Bottom right panel shows a 3D reconstruction of z-sections (27.3 µm overall, 0.7 µm/slice), of the framed area. (E) The distribution of CX₃CR1 and MHCII cells among the CD45.2⁺CD11b⁺ myeloid subsets of the CP at 3 dpi. (F,G) The frequency of CD11c⁺ cells among CX₃CR1⁺MHCII⁺ cells (top panels) and CX₃CR1⁻MHCII⁺ cells (bottom panels). (H) CD11c median fluorescent intensity (MFI) in CX₃CR1⁺MHCII⁺ and CX₃CR1⁻MHCII⁺ in mice that had been LPS preconditioned and ICV injected with activated Th1 cells. Each symbol represents one LV CP from an individual mouse. Bars represent means ± SEM. *P < 0.05, **P < 0.01, and ***P < 0.001, ****P < 0.0001 [(A–C,G) one-way ANOVA; (E) two-way ANOVA; (H) unpaired t test].