H1-receptor dependence of histamine-induced enhancement of human eosinophil C3b rosettes.

The pharmacological specificity of histamine-induced enhancement of human eosinophil C3b rosettes was studied using H1- and H2-receptor agonists and antagonists. The H1 agonist, 2-(2-aminoethyl) thiazole (2-2-AET), enhanced eosinophil C3b rosettes in a comparable fashion to that of histamine, whereas the H2 agonists, 4-methylhistamine and Dimaprit, were without effect. Similarly, rosette enhancement by histamine was inhibited by the H1 antagonists, chlorpheniramine and mepyramine, but not by the H2 antagonists, burimamide and metiamide. These experiments indicate that enhancement of eosinophil C3b rosettes by histamine, a mechanism which might be of importance in the amplification of complement-dependent killing of helminthic larvae, is predominantly H1-receptor-dependent.