Synovial fluid from patients with rheumatoid arthritis modulates monocyte cell-surface phenotype

Objectives: To investigate the ability of synovial fluid from patients with rheumatoid arthritis (RA) or osteoarthritis (OA) to modulate cell-surface phenotype, function and viability of monocytes. Methods: Monocytes from healthy donors were incubated with synovial fluid from patients with RA or OA. These were then cultured with autologous healthy CD4+ T-cells. Immunoglobulin-like transcript 4 (ILT4) and CD86 were evaluated on stimulated monocytes and CD4+ T-cells via fluorescence activated cell sorting. Results: Monocytes incubated with synovial fluid from patients with RA (SF-RA; n = 12) had significantly lower ILT4 and higher CD86 levels than those incubated with synovial fluid from patients with OA (SF-OA; n = 12) or medium alone. In patients with RA, there was a significant negative correlation between ILT4 and disease activity score (DAS; r = −0.699), and a positive correlation between CD86 and DAS (r = 0.626). T-cells costimulated with monocytes cultured with SF-RA produced significantly more interferon-γ and tumour necrosis factor-α than those costimulated with monocytes cultured with SF-OA or controls. Conclusions: Soluble mediators in SF-RA could contribute to modulating inflammation and local effectiveness of the immune response.