To determine distribution of T cells and activation degree of Th CD4+ cells in peripheral blood of patients with osteoarthritis (OA), rheumatoid arthritis (RA), and healthy donors.

Patients with established diagnosis of RA according to American College of Rheumatology/European League Against Rheumatism 2010 criteria, knee or hip OA according to American College of Rheumatology criteria, and healthy blood donor volunteers were eligible. Multi-channel flow cytometry and monoclonal antibodies against CD3, CD4, CD8, CCR6, CD38, CXCR3, and HLA DR were used to distinguish and evaluate T cells’ subpopulation.

We analyzed blood samples of 15 patients with well-defined RA, 56 with hip or knee OA, and 20 healthy age matched controls. Blood samples from RA patients showed significantly higher counts of CD4+ CD38+ DR+ (activated CD4 T cells) and Th17 (CCR6+ CXCR3−) cells as compared to OA patients and control group (P<0.01). Furthermore the samples from the OA patients showed a higher percentage of activated CD4 T cells and Th17 cells as compared to control group (P<0.05). Interestingly there was no difference between Th1 (CD4+ CXCR3+ CCR6−) and Th2 (CD4+ CXCR3− CCR6−) between the three groups (P>0.1).

According to the latest view of OA disease pathogenesis, our preliminary results support the hypothesis that OA may also be a disease with an immunological/inflammatory involvement like RA. It seems that there is a quantitative but non-qualitative difference in Th17 cells’ profile, including the expression of activation markers, between RA and OA.