The aim of the study was to identify cell population which could be used as a marker predicting response to anti-TNF therapy. A total of 46 patients was analyzed, out of them: 23 patients with juvenile idiopatic arthritis (11 – Enbrel, 11– Remicade and 1– Humira), 16 patients with ankylosing spondylitis (8 – Enbrel, 8 – Remicade), 5 patients with rheumatoid arthritis (all Enbrel) and 2 patients with psoriatic arthritis (both Enbrel) and 19 controls. Clinical parameters (CRP, ESR, DAS28, BASDAI, VAS score, number of tender and swollen joints) from 11 patients with juvenile idiopatic arthritis and 3 with ankylosing spondylitis were available before and 3 months after onset of the therapy. Immunophenotyping of peripheral blood of patients and controls was performed using polychromatic flow cytometry. A population of CD19+CD20-CD27highCD38+CD138+ plasma cells was identified which significantly differed in the frequencies between responding and resistent patients (responders: 1.3–10.3%; median 7.04±1.05; 95%CI 4.06–9.03 vs. non-responders 17.3–37.3; median 27.75±9.18; 95%CI 18.12–37.38; p=0.0007). All responders showed statistically significant improvement of clinical parameters. The frequency of CD19+CD20-CD27highCD38+ CD138+ plasma cell population was found to be in responders at least 13-fold reduced in comparison to non-responders and this population might represent biological marker predicting the outcome of anti-TNF therapy

        Key words: anti-TNF, B-cells, plasma cells, flow cytometry, response to therapy