RU 41 740 (Biostim) and IL-4, or IL-13, have opposite effects on CD14, CD23, HLA-DR and HLA-DQ on monocytes.

RU 41 740 (Biostim) is a glycoprotein extract obtained from Klebsiella pneumoniae. Its immunostimulating properties on monocytes have been established in vivo and in vitro. To confirm its spectrum of action at molecular level we studied its role on the modulation of four molecules involved in antigen presentation (HLA-DR, HLA-DQ), uptake of endotoxin (CD14) and activation (CD23). These four molecules are known to be modulated by interleukins IL-4 and IL-13. We found that HLA-DR, HLA-DQ, CD14 and CD23 were differentially regulated by biostim and IL-4 or IL-13. Surprisingly, Biostim inhibited the IL-4 or IL-13-induced expression of CD23, HLA-DQ and HLA-DR, while it did not have any action on these molecules by itself. We therefore hypothesize that Biostim, through the action on its receptor, could interact with the IL-4 receptor and IL-13 receptor and/or inhibit the IL-4 and IL-13 receptor transducing signal.