Proliferation of pannus tissue cells in rheumatoid arthritis.

Proliferation of pannus tissue cells has been investigated under in vitro conditions after labeling of joint tissues with 3H-thymidine. It was demonstrated that there is only a minimal proliferation of chondrocytes as well as of pannus tissue cells. Slight increased proliferation was observed in granulation tissue poor in lymphocytes and plasma cells, and perhaps in those areas of destroying pannus tissue that exhibited polymorphonuclear granulocytes (PMNs) at the pannus-cartilage junction. These results are in contrast to the idea that pannus tissue is a tumor-like lesion, for the present observations, even within the limits of autoradiographic investigations on a heterogeneous tissue, and indicate that pannus tissue has to be regarded as an inflammatory granulation tissue.