IL-1β is rarely expressed by spinal cord–resident leptomeningeal macrophages and microglia. (A) Representative image of the lumbar spinal cord of a CX₃CR1-Cre^ERT2::Rosa26-TdT mouse shows that leptomeningeal macrophages from the dura, arachnoid, and pia maters are expressing TdT. (B) Immunofluorescence staining of the spinal cord of a CX₃CR1-Cre^ERT2::Rosa26-TdT mouse at the peak of EAE disease is shown. IL-1β protein expression and infiltrating myeloid cells (CD11b⁺ TdT⁻), as well as resident leptomeningeal macrophages and microglia (CD11b⁺ TdT⁺), are shown. (C) Immunofluorescence staining of the spinal cord of a CX₃CR1-Cre^ERT2::Rosa26-TdT::LysM-GFP triple transgenic mouse at the peak of disease. IL-1β and infiltrating myeloid cells (GFP⁺ TdT⁻), as well as leptomeningeal macrophages and microglia (GFP⁻ TdT⁺), are shown. White arrowheads indicate colocalization with GFP. Bars: (A) 50 µm; (B and C) 20 µm.