title: The ultrastructural localization of fibronectin in the lining layer of rheumatoid arthritis synovium: the synthesis of fibronectin by type B lining cells.
abstract: The distribution of fibronectin in the lining layer of inflamed rheumatoid arthritis (RA) synovium has been ultrastructurally investigated using an anti-human plasma fibronectin antibody. The hyperplasia of lining cells was prominent in the lining layer of the inflamed RA synovium. A high level of fibronectin was localized in this region. Ultrastructurally the fibronectin was observed on the surface of both type A (type M) and type B (type F) cells, and in the extracellular fibrin-like material. This glycoprotein was detectable in rough endoplasmic reticulum (RER), some Golgi apparatus, and peripheral vesicles of type B cells. On the other hand, RER and Golgi apparatus of type A cells failed to be immunostained with the antibody. Type A cells occasionally contacted each other with interdigitation of cytoplasmic processes, and a high amount of fibronectin was localized in this region. These findings indicate that fibronectin is synthesized along the classic secretory pathway through RER and Golgi apparatus of type B cells. On the contrary, type A cells seem not to be associated with the local synthesis of the glycoprotein. Fibronectin may play a structural role in organizing these proliferated lining cells by promoting cell adhesion. The synthesis of fibronectin by proliferated type B cells may be responsible in part for the local increase of this glycoprotein in the lining layer of RA synovium.
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005353:Fibronectins / Q000096:biosynthesis*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D013583:Synovial Membrane / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D005353:Fibronectins