Effects of cetirizine on human eosinophil and neutrophil activation in vitro

The ability of cetirizine, a novel antihistamine agent, to inhibit the in vivo activation of human eosinophils, neutrophils and monocytes has been investigated using C3b- and IgG-dependent rosette formation, cytotoxicity against opsonised parasitic larvae and adherence to plasma-coated glass (PCG). The drug inhibited platelet-activating factor (PAF)-induced enhancement of eosinophil and neutrophil IgG (Fc) and complement (C3b) rosettes with an IC50 of 2 x 10(-5) M. There was also comparable inhibition of PAF-dependent enhancement of eosinophil cytotoxicity (for complement-coated schistosomula of Schistosoma mansoni). Cetirizine inhibited PAF-induced eosinophil, but not neutrophil, hyperadherence to PCG. These data support the view that cetirizine may exert some of its anti-allergic effects by inhibiting the activation of human granulocytes and that it may also selectively inhibit PAF-induced eosinophil hyperadherence.