Involvement of α4-integrin and VCAM-1 in permanent T lymphoblast adherence within spinal cord white matter microvasculature. (a–d) Permanent T lymphoblast adherence in control mice 10 minutes after cell injection. T cell blasts were permanently adherent either within the capillary network (a and b) or within postcapillary venules (c and d). Intravital fluorescence videomicroscopy using epi-illumination techniques. Contrast enhancement of spinal microvasculature using FITC-dextran₁₅₀ (a and c; arrows mark localization of T cells). Cell Tracker Orange–labeled T lymphocytes (b and d). Bar, 100 μm. (e–j) Permanent T lymphoblast adherence 1 hour after cell injection. Control (e and f), anti–α4-integrin Ab (g and h), anti–VCAM-1 (i and j). Intravital fluorescence videomicroscopy using epi-illumination techniques. Contrast enhancement of spinal microvasculature using FITC-dextran₁₅₀ (e, g, and i; arrows mark localization of T cells). Cell Tracker Orange–labeled T lymphocytes (f, h, and j). Bar, 100 μm. (k) Quantitative analysis of permanent T lymphoblast adherence. T lymphoblasts permanently adhering within spinal cord white matter microvasculature were counted 10 minutes, 1 hour, and 2 hours after infusion of 3 × 10⁶ PLP-specific T cell blasts by intravital fluorescence videomicroscopy using epi-illumination techniques as described in Methods. Number of mice included in this analysis per group: control, n = 5 mice; antibody-control, n = 2 mice; anti–α4-integrin group, n = 3 mice; and anti–VCAM-1 group, n = 3 mice. Asterisks indicate significant differences. p.i., postinjection.