Ligation of CD23 activates soluble guanylate cyclase in human monocytes via an L-arginine-dependent mechanism.

Transduction through Fc epsilon R2/CD23 was analyzed in normal human monocytes using immunoglobulin E (IgE)-anti-IgE immune complexes (IgE ICs) and monoclonal antibodies (mAbs) to CD23. Anti-CD23 mAb and IgE IC triggered a time-dependent increase in cGMP and cAMP in interleukin-4-preincubated (CD23+) but not in unstimulated (CD23-) monocytes. Maximal cGMP and cAMP accumulations were observed 10 and 20 min, respectively, after the onset of CD23 ligation. The increase in cGMP was inhibited with N omega-monomethyl-L-arginine (L-NMMA), which also partially affected cAMP accumulation. Addition of an anti-CD23 mAb Fab fragment inhibited the IgE IC- and the anti-CD23 mAb-induced cGMP and cAMP accumulation, confirming the engagement of CD23. In addition, IgE IC and anti-CD23 mAb induced, at least in some donors, a production of nitrite that was inhibited in the presence of L-NMMA. Taken together, these findings suggest a possible involvement of the nitric oxide synthase pathway in IgE IC-mediated activation of CD23+ monocytes.