Leukocyte extravasation across the blood-brain barrier is a critical event in the pathogenesis of multiple sclerosis (MS). This complex multistep process includes the adhesion of leukocytes to the endothelial cells of the central nervous system microvasculature. To investigate this phenomenon in MS, we developed a modified version of the frozen-section assay. Peripheral blood mononuclear cells (PBM) from 26 MS patients, 26 healthy controls and 10 patients with other inflammatory non- neurological diseases (OIND) were co-incubated with cryostat sections of normal brain white matter, immunohistochemically labelled with anti-CD45 antibody and counterstained with Giemsa stain. CD45-positive PBM adherent to transected microvasculature were counted with an automated image analyzer. MS patients showed an increased number of vessel-bound PBM (48.8 +/- 36.4) with respect to healthy controls (27.4 +/- 20.7, P = 0.01) and OIND patients (22.6 +/- 7.8, P = 0.01). Significant differences were also obtained counting the number of vessel-bound PBM as a percent of total vascular cells between MS patients (12.7 +/- 7.2%) and healthy controls (6.9 +/- 5.4%, P = 0.002) or OIND patients (7.4 +/- 4.4%, P = 0.03). We confirm that PBM from MS patients show an increased potential of binding to cerebral vessels. The frozen-section assay provides a unique tool to study in situ the molecular interactions of leukocytes with brain vascular structures.
Copyright Lippincott Williams & Wilkins