The aim was to investigate CD4
Peripheral blood, synovial fluid (SF) and synovial membranes (SM) of RA and OA patients were analyzed. CD4
In peripheral blood, OA patients had altered frequencies of regulatory T-cell subsets, and higher frequencies of Th17 and of Th1/17 cells than RA patients. In the synovial compartment of OA patients, conventional Th17 cells were largely excluded, while Th1/17 cells were enriched and more frequent than in RA patients. Conversely, in the synovial compartment of RA patients, regulatory T cells and Tfh cells were enriched and more frequent then in OA patients. IL-17 and Blys were increased both in serum and SF of RA patients, and correlated with autoantibodies and disease activity. Notably, Blys levels were already significantly elevated in RA patients with low disease activity score in 28 joints (DAS28) and without autoantibody positivity.
Although patients with inflammatory OA have immune activation in the synovial compartment, they display different T-cell subset frequencies and cytokine profiles. Soluble mediators such as Blys might help to discriminate mild clinical forms of RA from inflammatory OA particularly at the onset of the disease.