Preliminary study on immune cells in the synovium of end-stage osteoarthritis and rheumatoid arthritis patients: neutrophils and IgG4-secreting plasma cells as differential diagnosis candidates.

OBJECTIVE

Immune cell evaluation could be useful for clarifying etiopathogenesis, providing a support for formulating the diagnoses of clinically similar joint pathologies or guiding indications for possible therapeutic targets. To contribute to differential diagnosis in joint pathologies we performed an immunophenotypical profile analyzing different immune cells in synovial tissues from patients with rheumatoid arthritis (RA) and osteoarthritis (OA).

METHODS

The Krenn and immunologic synovitis (IMSYC) scores, which include the evaluation of T lymphocytes (CD3 positive), B lymphocytes (CD20), endothelial cells (CD31), macrophages (CD68) and proliferating cells (Ki-67 positive) were used to analyze the synovial tissue samples. Moreover, to corroborate immune activation, neutrophils (CD15 positive), NK cells (CD56 positive), plasma cells (CD138 positive), IgG4 and IgG4 secreting-CD138 cells were analyzed using immunohistochemical techniques.

RESULTS

We confirmed that all the samples had a high synovitis score according to both the Krenn and IMSYC scores. In both the RA and OA groups, we found similar scores for CD3 (T lymphocytes), CD20 (B lymphocytes), CD31 (endothelial cells), CD56 (NK cells), CD68 (macrophages) CD138 (plasma cells) and IgG4. In contrast, CD15 (neutrophils) was significantly higher in RA compared to OA. Interestingly, IgG4 secreting-CD138 cells were significantly higher in RA than OA, even if CD138 had the same score in both the RA and OA samples.

CONCLUSIONS

This study found that the scores for different immune cells were similar in both RA and OA synovial tissue with a high synovitis score. CD15 and IgG4 secreting-CD138 were the only immune cells with a higher score in RA compared to OA, suggesting a potential use for discriminating among pathologies with a high synovitis score.