Ankylosing Spondylitis and Rheumatoid Arthritis: Serum Levels of TNF-α and Its Soluble Receptors during the Course of Therapy with Etanercept and Infliximab

The effects of the TNF-α blockers infliximab or etanercept on the levels of TNF-α, TNF-receptor 1 (TNF-R1), and TNF-receptor 2 (TNF-R2), as well as the levels of the inflammation markers CRP and IL-6, were measured in ankylosing spondylitis (AS) and rheumatoid arthritis (RA) patients receiving treatment with either compound. We found that RA patients tend to have higher levels of TNF-α than both healthy individuals and AS patients prior to treatment (P < 0.05). We measured greatly increased levels of TNF-α in both the AS and RA etanercept patient groups during the course of treatment, while in the infliximab treated patients, the amount of TNF-α measured remained unchanged. Elevated TNF-α in the etanercept treated patients does not appear to be a significant risk factor for the spontaneous development of further autoimmune diseases in our study group. Increased levels of TNF-R1 were determined in both AS (P < 0.05) and RA (P < 0.001) patients when compared to healthy controls. In AS patients, the levels of TNF-R1 dropped significantly when treated with either infliximab (P < 0.01) or etanercept (P < 0.001). In contrast, the levels of this receptor remained unchanged in RA patients treated with either compound.