LMO2 T-ALL cells are present at multiple sites throughout the murine CNS and are colocalized with tumor-associated myeloid cells. (A-F) Representative immunofluorescent (IF) images of transplanted LMO2 T-ALL cells (CD5⁺; green) interspersed with myeloid subsets (IBA1⁺, red; F4/80⁺, blue) in multiple locations within the CNS of leukemic mice, with comparable regions of healthy control mice shown adjacent. Cryosections of brain and spinal tissue indicate the presence of T-ALL and myeloid cells in the dorsal hemisphere boundary (original magnification ×20) (A), the ventral hemisphere boundary (original magnification ×20) (B), the leptomeningeal spaces (original magnification ×20) (C), the perivascular spaces with CD31 (blue) demarcating vasculature (original magnification ×40) (D), the choroid plexus within the third ventricle (original magnification ×40) (E), and the meningeal layer (m.) surrounding the spinal cord (s.c.; original magnification ×40) (F). In panels A-F, scale bars represent 100 μm, unless otherwise indicated.