Metabolic studies of high-walled endothelium of postcapillary venules in rat lymph nodes

Functional and biosynthetic changes in endothelial cells of vessels in chronically inflamed tissues: evidence for endothelial control of lymphocyte entry into diseased tissues

In vitro lymphocyte adhesion to, and selective radiosulphate uptake by, endothelial cells has been demonstrated in chronically inflamed tissues of patients with peptic ulceration, rheumatoid disease, pilonidal sinus, autoimmune thyroiditis, polymyositis, primary biliary cirrhosis, and pyelonephritis. These characteristics have been described previously in endothelial cells functionally specialized for promoting lymphocyte traffic from blood to lymph node parenchyma. It is suggested that these observations indicate that some vessels in inflamed tissues may be, at least in part, responsible for the selective accumulation of lymphocytes within the tissue. Manipulating the development of this type of vessel may offer a novel way of influencing the progress of inflammatory disorders.

Molecules controlling lymphocyte-endothelial interactions in lymph nodes are produced in vessels of inflamed synovium

In vitro lymphocyte adhesion to, and selective radiosulphate uptake by, endothelial cells has been demonstrated in diseased synovium of patients with rheumatoid disease, osteoarthritis, and the peripheral arthropathy associated with ankylosing spondylitis and ulcerative colitis. These characteristics have been described previously in endothelial cells functionally specialised for promoting lymphocyte traffic from blood to lymph node parenchyma. It is suggested that these observations indicate that some synovial vessels may be responsible, at least in part, for the selective accumulation of lymphocytes in the tissue. Manipulation of the development of this type of vessel may offer a novel way of influencing the progress of inflammatory arthropathies.

Blood vessels of the Peyer's patch in the mouse: III. High-endothelium venules

High-endothelium venules of mouse Peyer's patches were examined by scanning electron microscopy, and a quantitative assessment was made of the location of lymphocytes in relation to endothelial cells. Untreated mice and mice with markedly depressed levels of circulating lymphocytes were used. Lymphocytes were divided into adhering and migrating cells and as to association either with the body of the endothelial cell or with its cell border. Over 90% of all adhering cells and the great majority of migrating lymphocytes were located at the cell border. The exception was one animal in which most migrating lymphocytes appeared to penetrate the endothelial cells. Our data lend strong support to the currently held view that most migrating lymphocytes traverse the endothelium by following an intercellular path but that, under certain conditions, lymphocytes may penetrate the cytoplasm of endothelial cells.

Blood vessels of the Peyer's patch in the mouse: II. In vivo observations

A technique was developed that allowed the in vivo observation of Peyer's patches in the mouse for several hours. Untreated animals and animals depleted of lymphocytes were used. In this species, blood vessels associated with the lymphoid nodules are readily visible through the thin serosal muscle coat. High-endothelium venules are recognized by the large number of refractile cells that adhere to the luminal surface. A colloidal carbon suspension injected intravenously labeled high-endothelium venules and was only rarely seen in arterial and capillary segments or in venules of the gut parenchyma. When fluorescein isothiocyanate-labeled (FITC-labeled) syngeneic spleen cells were injected, they appeared in vessels of the Peyer's patch within a few seconds and began to adhere to the luminal surface of high-endothelium venules. In untreated animals, peak numbers of fluorescent cells were reached after about 20 min. Many adhered but some were swept away. In lymphocyte-depleted animals, however, peak numbers were reached after only a few minutes and most cells remained attached.

A possible route for lymphocyte migration into diseased tissues

Vessels within the lymphocytic infiltrate in 161 examples of 24 different diseases have been studied using light and electron microscopy and histochemistry. Hitherto undescribed venules have been identified within lymphocyte aggregates which exhibit a structure, ultrastructure and cytochemistry previously believed to be restricted to the high endothelial venules of lymphoid tissues. The significance of these findings is discussed within the context of lymphocyte migration into abnormal tissue.