Electron microscopic study of rheumatoid synovial vasculature: intimate relationship between tall endothelium and...

A relationship has been demonstrated between the tallness of the endothelial cells (EC) of the postcapillary venules (PCV) of rheumatoid (RA) synovial membrane and the cellular composition of adjacent perivascular mononuclear cell infiltrates. A strong positive correlation between EC tallness and the number and percent of perivascular lymphocytes was observed. In contrast, EC tallness showed negative correlations with percent perivascular plasma cells, macrophages and fibroblasts. None of the preceding correlations were observed in the case of pericapillary infiltrates. The findings obtained indicate that the PCVs of the RA synovial membrane, from which lymphocytes emigrate to form perivascular lymphoid aggregates, resemble the tall endothelial PCVs of normal lymphoid tissue. They suggest that chronic inflammatory tissue and normal lymphoid tissue share common mechanisms of lymphoid emigration.