Histamine Upregulates Th1 and Downregulates Th2 Responses due to Different Patterns of Surface Histamine 1 and 2 Receptor Expression

Histamine, which acts via G protein-coupled receptors, is an important mediator of immediate hypersensitivity and is also able to influence the nature of T cell responses. We demonstrated that TH1 and Th2 cells express distinct surface histamine receptor patterns and that Th1-type responses are enhanced by histamine, whereas Th2-type responses are negatively regulated, due to different intracellular signals generated by histamine stimulation. These findings account for negative feedback regulation in a wide variety of pathologies.