[The therapeutic blockade of TNF reduces serum levels of interleukin 15 in patients with rheumatoid arthritis].

OBJECTIVE To analyze the effect of the TNF blocking agents (aTNF) on the serum levels of interleukin 15 (IL-15). To determine whether baseline IL15 serum levels or their response to aTNF therapy can predict the clinical response to this treatment. PATIENTS AND METHOD We studied 75 patients suffering from rheumatoid arthritis that were selected to start aTNF therapy. Serum samples were obtained at baseline visit and after three months of aTNF treatment. Measurement of IL-15 serum concentration was performed through immune-enzyme assay. We collected the clinical and analytical parameters needed to calculate DAS28 both at baseline and final visit, as well as sociodemographic variables and other such as rheumatoid factor, previous disease modifying anti-rheumatic drugs (DMARD), etc. We defined remission as a DAS28 < 2.6 and clinical response when the decrease in DAS28 value was higher than 1.2. RESULTS There was a significant correlation between IL-15 serum level and the number of previous DMARD. We also detected a significant decrease in the concentration of serum IL-15 after three months of treatment with aTNF. However, neither the baseline IL-15 serum level nor the decrease in the concentration of IL-15 were associated with a specific pattern of response to aTNF. CONCLUSIONS Our data seem to support previous in vitro findings suggesting that TNF is involved in the regulation of IL-15 expression. Nevertheless, the measurement of IL-15 serum levels does not seem to be a useful tool to select those patients that should be treated with aTNF therapy.