Several clinical studies performed with human recombinant interleukin 10 (IL-10) in patients with rheumatoid arthritis (RA) have shown little efficacy. We investigated potentially proinflammatory in vivo effects of IL-10 in humans. We evaluated the upregulation of Fc gamma receptor (Fc gamma R) expression on monocytes/macrophages (and granulocytes) in patients with RA receiving different dosages of IL-10.
Together with changes in disease activity and several cell markers, the expression of Fc gamma RI, Fc gamma RIIa, and Fc gamma RIII was determined on granulocytes and monocytes/macrophages from the peripheral blood of 6 patients with active RA before and after treatment with recombinant human IL-10. In addition, the in vitro effect of IL-10 on Fc gamma R expression on monocytes/macrophages in combination with their susceptibility to immune complex induced production of tumor necrosis factor-alpha(TNF-alpha) was assessed.
Clinical improvement was not observed in the IL-10 treated patients (based on ACR20 criteria). Significant decreases in thrombocyte numbers were observed in patients receiving IL-10. No changes in cell markers such as CD14 were found. On the other hand, expression of Fc gamma RI and Fc gamma RIIa on monocytes/macrophages was increased upon high dose IL-10 treatment. Interestingly, increases in expression of Fc gamma RI and Fc gamma RIIa correlated with a decrease in thrombocyte numbers. In vitro, IL-10 similarly upregulated Fc gamma RI and Fc gamma RIIa expression on monocytes/macrophages from RA patients. This was accompanied by increased TNF-a production after immune complex stimulation.
These findings indicate that upregulation of Fc gamma R expression in RA with IL-10 treatment may counteract the otherwise antiinflammatory effects of IL-10 by potentiating immune complex mediated proinflammatory responses.