Objective: To investigate the nuclear localization of the transcription factor NF-kappa B, the status of apoptosis and the expression of the Fas antigen, Fas ligand, Bcl-2, Bcl-xL and Bax by synovial cells.
Methods: Electrophoresis mobility shift assay (EMSA), immunohistochemical staining, two colour-flow cytometry and the terminal deoxynucleotidyl transferase (TDT)-mediated dUTP nick end labelling (TUNEL)-technique were used.
Results: The NF-kappa B p65 subunit appears to be present in the nuclei of synovial tissue and fluid cells as detected by EMSA and immunohistochemical staining. Fas antigen and Fas ligand (L) are expressed on up to 90% and 11% of CD3+ synovial fluid (SF) cells, respectively. Both the Fas antigen and its ligand are also expressed by synovial tissue cells. Interestingly, freshly isolated SF T cells upregulated the expression of Bcl-xL as compared to Bcl-2. An overexpression of Bax compared to Bcl-xL was seen in the synovial tissues (ST) of patients with ongoing apoptosis, but not in patients with few apoptotic cells.
Conclusions: NF-kappa B appear to be activated in vivo, both Fas and its ligand being expressed by synovial cells. Apoptosis is ongoing in the ST with significant patient variations. Such variations could be in part due to the level of Bax expression. Finally, the upregulation of Bcl-xL expression may contribute to the accumulation of SF infiltrating T cells.