Distinct and mutually exclusive Ca2+ flux-and adenylyl cyclase-inducing gene expression profiles of G-protein-coupled receptors on human antigen-specific B cells

B cells play an essential role in allergies by producing allergen-specific IgE, which is a prerequisite for allergen-induced degranu-lation of mast cells (MCs) and basophils. MCs, basophils, dendriticcells and bacteria are capable of secreting inflammatory mediatorsincluding histamine.1 Histamine is a bioactive amine that exerts itsfunction through binding to histamine receptors (HRs), which are7-transmembrane G-protein-coupled receptors (GPCRs). Histaminecan regulate its function through four receptors (HR1-HR4), in whichligation of histamine with HR1 can trigger Ca 2+ mobilization, whereasHR2 stimulates and increases cAMP concentrations. 2 Interestingly,HRH1 and HRH2 genes can show mutually exclusive expression pat-tern in B cells, with a differential antibody response as demonstratedin the clones.