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Aims-To examine the vascular changes occurring in three archival cases of acute multiple sclerosis, and to provide immunohistochemical evidence of early endothelial cell activation and vascular occlusion in this condition. Methods-Central nervous system tissues from three cases of acute active multiple sclerosis and six non-inflammatory controls were stained using the following methods: haematoxylin and eosin, Luxol fast blue, cresyl violet, Bielschowsky's silver, and reticulin. Tissues were also inmunostained with specific antibodies against collagen type IV, factor XIIIa, class II antigens, glial fibrillary acidic protein, and fibrinogen. Results-Early vascular endothelial cell activation which may progress to vasculitis and vascular occlusion including class II antigen expression and fibrin deposition were identified. The vascular changes were seen prior to cerebral parenchymal reaction and demyelination, and were not seen in control cerebral tissues.Conclusion-It is proposed that vascular endothelial cell activation may be an early and pivotal event in the evolution of multiple sclerosis, and that demyelination may have an ischaemic basis in this condition. The vascular endothelium may contain an early element in the evolution of multiple sclerosis. (J Clin Pathol 1994;47:129-133) Academic

No abstract

Aphthoid ulceration has been regarded as an early macroscopic feature of Crohn's disease, yet the cause ofthis mucosal lesion is unknown. Examination of areas of apparently normal and non-inflamed bowel in Crohn's disease has allowed the identification of mucosal changes which occur before macroscopic and microscopic ulceration. Thirty five resection specimens from patients with Crohn's disease were compared with 12 specimens from patients with ulcerative colitis and 13 controls. Specimens were fixed either by immersion in formalin in the routine way or by perfusion fixation with formalin at mean arterial pressure. Immunostaining for macrophages, vessel wall, and blood constituents allowed identification of small mucosal capillaries which were not apparent otherwise. In Crohn's disease damage and rupture of these small capillaries occurred before infiltration of the lamina propria by inflammatory cells. Loss of the overlying epithelium seemed to follow this vascular damage.