Cyclooxygenase-Derived Prostaglandin E2 Drives IL-1-Independent Mycobacterium bovis Bacille Calmette-Gue acute accent rin-Triggered Skin Dendritic Cell Migration to Draining Lymph Node

Inoculation of Mycobacterium bovis Bacille Calmette-Guerin (BCG) in the skin mobilizes local dendritic cells (DC) to the draining lymph node (dLN) in a process that remains incompletely understood. In this study, a mouse model of BCG skin infection was used to investigate mechanisms of skin DC migration to dLNs. We found enhanced transcription of cyclooxygenase (COX)-2 and production of COX-derived PGE(2) early after BCG infection in skin. Animals treated with antagonists for COX or the PGE(2) receptors EP2 and EP4 displayed a marked reduction in the entry of skin DCs and BCG to dLNs, uncovering an important contribution of COX-derived PGE(2) in this migration process. In addition, live BCG bacilli were needed to invoke DC migration through this COX- PGE(2) pathway. Having previously shown that IL-1R partially regulates BCG-induced relocation of skin DCs to dLNs, we investigated whether PGE(2) release was under control of IL-1. Interestingly, IL-1R ligands IL-1 alpha/beta were not required for early transcription of COX-2 or production of PGE(2) in BCG-infected skin, suggesting that the DC migration-promoting role of PGE(2) is independent of IL-1 alpha/beta in our model. In DC adoptive transfer experiments, EP2/EP4, but not IL-1R, was needed on the moving DCs for full-fledged migration, supporting different modes of action for PGE(2) and IL-1 alpha/beta. In summary, our data highlight an important role for PGE(2) in guiding DCs to dLNs in an IL-1-independent manner.

Automated summary

This study found that Mycobacterium bovis Bacille Calmette-Guerin (BCG) vaccination induces the migration of dendritic cells (DCs) from the skin to the draining lymph nodes (dLNs) through the production of cyclooxygenase (COX)-derived PGE(2). Live BCG bacilli are necessary for this migration process. It was also found that IL-1 is not required for the early production of COX-2 or PGE(2) in BCG-infected skin, suggesting an IL-1-independent role for PGE(2) in DC migration. Furthermore, EP2/EP4, but not IL-1R, on DCs were shown to be important for the migration process.