THE DISTRIBUTION AND ABNORMAL MORPHOLOGY OF PLASMA-CELLS IN RHEUMATOID SYNOVIUM

This study assessed the distribution and structural features of plasma cells in rheumatoid synovial tissue. Plasma cells were found to be th e predominant infiltrating mononuclear cells (mean 40%) in relation to lymphocytes and monocytes, and there was a direct relationship betwee n their number in the infiltrates and the total number of mononuclear leucocytes (P = 0.007). Plasma cells were also seen in intimate contac t with macrophages intermixed with synovial lining cells, and closely associated with small blood vessels. They often surrounded these blood vessels and sometimes were seen lying within the vessel walls themsel ves. Ultrastructural analysis revealed that many synovial plasma cells were considerably larger than plasma cells of a normal size and posse ssed a marked distension of the cisternae of rough endoplasmic reticul um. Furthermore, plasma cells in close proximity to blood vessels ofte n appeared to be undergoing migration. These observations imply that i n rheumatoid synovium, plasma cells are metabolically very active and occupy a pivotal position for the secretion of antibodies into both th e vascular and the extravascular compartments.