OVA-A ⁵⁵⁵ tracer distribution after ICM and intraspinal injection. (A) Coronal section of the cervical spine after ICM injection of OVA-A⁵⁵⁵ (white). Note that OVA-A⁵⁵⁵ spillover labeled paravertebral tissues (PVT, arrowhead) and the brainstem (BS). Asterisk, vertebral body. (B) FITC-dextran tracer distribution 45 min after Th-Lb or Lb-Sa injection. Macroscopic imaging of tracer labeling (white arrowheads) along the caudorostral axis of the spine. SC, spinal cord. (C–F) Coronal sections of the sacral (C and D) and cervical (E and F) spine showing ink deposits (black) in the meninges along the caudorostral axis. Macroscopic imaging of dissected spine segments (C and E) and bright-field microscopic imaging of paraffin-embedded spine sections (D and F). (G) Coronal section of the brainstem (BS) showing ink deposits in the meninges and inside the dcLNs (green arrowheads). Asterisk, vertebral body. (H) Sagittal section of the forehead showing ink deposits in the meninges of the olfactory bulb (OB), in the cribriform plate (CP), the olfactory epithelium (OE), and the nasopharynx (NP). Cx, cortex. (I) LSFM coronal view of the CSF tracer pattern (OVA-A⁵⁵⁵, white) in the perivascular spaces of the cortex and mesencephalon, and in the scLNs (green arrowheads). (J) Table of additional tracer injection experiments showing the number of mice per group with tracer-labeled cervical LNs 45 and 90 min after injection. (K) Representative flow dot plots used to separate different populations of OVA⁴⁸⁸⁺ myeloid cells in cervical LNs in Fig. 1, J and K. A, anterior; D, dorsal; L, lateral; P, posterior; V, ventral. Scale bar: 500 μm (B–F); 2 mm (A and G–I).