Presence of platelet glycoproteins Ib and IIb-IIIa in inflammatory and noninflammatory synovium.

Rheumatoid synovial tissue and noninflammatory synovial tissue from patients with meniscus lesions were stained using monoclonal antibodies against platelet 150 kDa Ib glycoprotein (gp Ib) and against 140/110 kDa IIb-IIIa glycoprotein complex (gp IIb-IIIa) applied with the avidin-biotin-peroxidase complex method. Gp Ib and gp IIb-IIIa positive intravascular platelet aggregates were not seen, except locally in the capillary blood vessels of one rheumatoid synovial sample. This suggests that the platelets and the clotting sequence are not activated in inflamed synovial tissue. However, in many of the synovial capillaries endothelial immunoreactivity was seen. This reaction could have been due to cross reaction, since the vitronectin receptor beta chain is structurally identical to platelet gp IIIa. The gp IIb-IIIa member of the integrin receptor family plays a role in the transmembrane linkage between its extracellular ligands and intracellular microfibers. Gp IIb-IIIa may thus contribute to normal synovial physiology and to the pathogenesis of chronic synovitis.