Ultrastructure of synovial changes in rheumatoid disease and in seronegative inflammatory arthropathies.

Synovial tissue has been examined by electron microscopy from patients suffering from either sero-positive or sero-negative inflammatory arthropathies to allow direct comparison of the ultrastructural changes found in these groups and to confirm and extend observations previously made in a smaller group of sero-negative arthropathies. Both groups have been compared with material from healthy controls. The sero-positive group comprised 13 cases of 'definite' or 'classical' rheumatoid arthritis. The sero-negative group consisted of 9 cases of arthritis secondary to Crohn's disease (3); Reiter's syndrome (2); Whipple's disease (1); Behcet's disease (1); Wegener's granulomatosis (1) and ankylosing spondylitis (1). The control tissue was obtained from 6 non-arthritic subjects undergoing surgery for non-inflammatory conditions. Confirmation was obtained of changes previously reported in subcellular organelles, especially in synovial B cells, in all forms of inflammatory arthritis as compared with controls. Attention is now drawn to other intracellular changes in B cells and intermediate cells which included: a marked increase of intermediate filaments and microfilaments: and proliferation of pinocytotic vesicles and rough endoplasmic reticulum. These changes were often accompanied by the presence, in the immediate environment of these cells, of extracellular microfibrillary masses but little or no accumulation of intermediate filaments. It was confirmed that synovial A cells were reduced in number but showed changes suggestive of increased phagocytic activity and also exhibited proliferation of cytoskeletal elements. Differences in these structural changes between sero-positive and sero-negative arthritis were of degree rather than of kind and no 'specific' or diagnostic differences were observed between the various forms of seronegative athropathies. The possible significance of the structural changes observed is discussed.