Differences in Ox40 expression by CD4+
T cells between NMO and MS lesions. Inflammatory lesions derived from spinal cords of NMO (A,B,C) and MS patients (D,E,F), and from brains of NMO (G,H,I) and MS patients (J,K,L) were reacted with antibodies specific for AQP4 (brown reaction product; counterstaining with hematoxylin reveals nuclei in blue; A,G), CD3 (brown reaction product; B,E,H,K), Ox40 (brown reaction product; C,F,I,L) or were stained with Kluever-Barrera to reveal myelin (blue; D,J). The spinal cord lesions shown are early active, as revealed by the large number of granulocytes in NMO (inlay in A) and by the presence of myelin degradation products in macrophages in MS (D). The brain lesions shown are late active in NMO, and early active, as revealed by macrophages containing myelin degradation products in MS (inlay in J). The inlays in I and L show Ox40+ T cells. In early active NMO lesions, 18% of all perivascular and 24% of all parenchymal OX40+ cells also express the proliferating cell nuclear antigen PCNA (M-O; PCNA visualized by the dark blue, Ox 40 by the brown reaction product).