Multiple biopsy specimens from various parts of the synovial membrane were sampled under direct vision during arthroscopic surveying of the inflamed knee joints of 12 patients with various arthritides. Considerable variation in the macroscopic signs of inflammatory activity was found within the single joint. However, there was a highly significant correlation (P < 0.001) between local macroscopic signs of inflammatory activity and microscopic signs (by immunohistochemical analysis of the corresponding tissue sample). The profound intraarticular variation in inflammatory activity was seen irrespective of clinical diagnosis. An immunohistologic pattern comprising foci of T helper cells, associated immunoglobulin‐bearing cells, and HLA‐DR‐expressing dendritic cells was not specific for rheumatoid arthritis or any other diagnosis, but was found in the biopsy samples from sites that macroscopically demonstrated maximal inflammatory activity.

We studied 10 patients who had arthritis of the knee joint, but no other signs of rheumatic disease. The clinical diagnosis of osteoarthritis was corroborated by arthroscopic evidence of characteristic cartilage degeneration. Signs of inflammation were confined to areas of the synovial membrane that lay near the cartilage; thus, the major part of the joint cavity was not affected. The intensity of the synovial inflammation varied within the areas involved, but was always most pronounced in regions rimming the cartilage. Biopsy samples selected from regions of intensely inflamed synovium contained foci of T lymphocytes, which were bordered by immunoglobulin‐carrying B lymphocytes and plasma cells, as well as strongly HLA‐DR positive dendritic‐like cells adjoined to αLeu − 3a + T helper lymphocytes. In tissue samples taken from macroscopically noninflamed areas, only a few infiltrating lymphocytes were seen. Thus, the inflammatory synovial changes found in osteoarthritis appear to be anatomically restricted and of varied intensity but, when present, are microscopically indistinguishable from the changes that have been previously described as indicative of rheumatoid arthritis.

Antibodies to ribonucleoproteins (RNP) and to the Sni antigen in sera from patients with mixed connective tissue disease (MCTD) and systemic lupus erythematosus were studied using the techniques of immunioblotting and immunoprecipitation of U small nuclear RNPs. A cross-sectional study indicated that antibodies reacting with a 68K protein were associated with anti-RNP specificity in MCTD, but rarely occurred in systemic lupus erythematosus patients' sera. A longitudinal study demonstrated the persistence of MCTD blotting patterns over many years, and the subsequent disappearance of those specificities in sera from patients who were in prolonged remission.Patients with connective tissue diseases produce antibodies which react with various cellular components such as DNA, RNA, proteins, and _____ From the Karolinska Institute, Stockholm, Sweden and the University of MissouriXolumbia.