Electron and immunoelectron microscopic investigation of basal lamina thickening in synovial capillaries and post-capillary venules in rheumatoid arthritis.

Capillaries and post-capillary venules in the synovium obtained from 12 rheumatoid arthritis (RA) patients have been investigated by electron microscopy and immunoelectron microscopy with a monoclonal antibody against human type IV collagen, which is one of the major basal lamina (BL) components. The level of BL thickening in RA synovial vessels is roughly parallel with that of cellular exudation. The BL thickening may be due to excessive production of BL components, in which the accelerated rate of death and replenishment of endothelial cells and pericytes plays an important role. These cells may not only produce a single layer of BL in their life-time but also produce excessive amounts of BL components to make several layers in their life-time.