Reciprocal crosstalk between dendritic cells and natural killer cells under the effects of PGE2 in immunity and immunopathology

The reciprocal activating crosstalk between dendritic cells （DCs） and natural killer （NK） cells plays a pivotal role in regulating immune defense against viruses and tumors. The cytokine-producing capacity, Th-cell polarizing ability and chemokine expression, migration and stimulatory functions of DCs are regulated by activated NK cells. Conversely, the innate and effector functions of NK cells require close interactions with activated DCs. Cell membrane-associated molecules and soluble mediators, including cytokines and prostaglandins （PGs）, contribute to the bidirectional crosstalk between DCs and NK cells. One of the most well-known and well-studied PGs is PGE2. Produced by many cell types, PG E2 has been shown to affect various aspects of the immune and inflammatory responses by acting on all components of the immune system. There is emerging evidence that PGE2 plays crucial roles in DC and NK cell biology. Several studies have shown that DCs are not only a source of PGE2, but also a target of its immunomodulatory action in normal immune response and during immune disorders. Although NK cells appear to be unable to produce PGE2, they are described as powerful PGE2-responding cells, as they express all PGE2 E-prostanoid （EP） receptors. Several NK cell functions （lysis, migration, proliferation, cytokine production） are influenced by PGE2. This review highlights the effects of PGE2 on DC- NK cell crosstalk and its subsequent impact on immune regulations in normal and immunopathological processes.