Immunohistochemical changes in synovial tissue during the course of adjuvant arthritis.

OBJECTIVE

To study immunohistochemical changes occurring in knee synovial membranes of rats during the time course of adjuvant arthritis (AA). The effect of treatment with dexamethasone after establishment of arthritis was also studied.

METHODS

AA was induced in Wistar rats by means of a single injection of a suspension of Mycobacterium butyricum. On Days 7, 14, 17, 21, 28 and 42 after induction, synovial membranes were obtained, frozen and sectioned on a cryostat. Tissue sections were tested by peroxidase-antiperoxidase method, using the following monoclonal antibodies: OX19 (CD5), W3/25 (CD4), OX8 (CD8), OX6 (Ia), OX33 (LCA) and OX39 (CD25).

RESULTS

Knee synovial membranes obtained from arthritic rats on days of maximum inflammation showed few or no CD5+ cells, a higher proportion of CD8+ cells, and a higher number of CD4+ and Ia+ cells than healthy synovial tissues. CD25+ cells were observed from Day 7 postinduction and remained numerous throughout the study.

CONCLUSION

Few T lymphocytes (CD5+) were found in arthritic synovial membrane, whereas an increase of cells expressing CD8, CD4, CD25, Ia, and LCA was found. These increases (except CD8) are not evident in dexamethasone treated rats.