Fig 2. Histopathological features of CIDP.

Digital photomicrographs of Toluidine Blue/ Basic Fuchsin stained plastic-embedded axial semi-thin sections from patients with CIDP show intense endoneurial mononuclear cell infiltrates with severe axonal loss (a). Reduced axonal density with a moderate number of thinly myelinated large and small diameter axons is a common feature of CIDP (b). Endoneurial accumulation of mononuclear leukocytes (c) may be seen. Indirect immunohistochemistry of frozen longitudinal thick sections with counterstained with Hematoxylin shows endoneurial CD68+ monocyte/macrophages (d; black arrows) closely associated with large diameter myelinated axons (white asterisks) suggestive of focal demyelination. Onion-bulb formation, indicative of repetitive demyelination and remyelination in chronic CIDP cases is shown (e and f), with endoneurial microvessel basement membrane thickening (g; black arrows) associated with reduced axonal density and increased endoneurial edema. A digital electron ultramicrograph of a sciatic nerve endoneurial microvessel within the inflammatory milieu of a 40 week old female CD86 deficient non-obese diabetic mouse with SAPP for 18 weeks shows intact electron-dense intercellular tight junctions (h; black arrows) with a cluster of pinocytic vesicles (PV), with an endoneurial microvessel intercellular tight junction from an age matched control mouse for comparison (i; black arrow). L indicates the vessel lumen and BM the basement membrane (h and i). Magnification bars: a and d= 50 μm; b = 100 μm; c = 10 μm; e and f = 5 μm; g = 25 μm; h and i = 200 nm