Cutting Edge: Cyclooxygenase-2 Activation Suppresses Th1 Polarization in Response toHelicobacter pylori

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Abstract
Helicobacter pylori infection causes a Th1-driven mucosal immune response. Cyclooxygenase (COX)-2 is up-regulated in lamina propria mononuclear cells in H. pylori gastritis. Because COX-2 can modulate Th1/Th2 balance, we determined whether H. pylori activates COX-2 in human PBMCs, and the effect on cytokine and proliferative responses. There was significant up-regulation of COX-2 mRNA and PGE2 release in response to H. pylori preparations. Addition of COX-2 inhibitors or an anti-PGE2 Ab resulted in a marked increase in H. pylori-stimulated IL-12 and IFN-γ production, and a decrease in IL-10 levels. Addition of PGE2 or cAMP, the second messenger activated by PGE2, had the opposite effect. Similarly, stimulated cell proliferation was increased by COX-2 inhibitors or anti-PGE2 Ab, and was decreased by PGE2. Our findings indicate that COX-2 has an immunosuppressive role in H. pylori gastritis, which may protect the mucosa from severe injury, but may also contribute to the persistence of the infection.