In the natural resolution of an anti-inflammatory response the inflammation is reduced via mechanisms that differ from inhibition of active inflammation. In July Nature Immunology, Bruce Levy and colleagues from Harvard Medical School, Boston, explain the molecular basis for events in the resolution of acute inflammation and suggest that inflammation itself signals a halt to mounting immune responses.

Levy et al. conducted temporal analyses of leukotrienes (LTs) and prostaglandins (PGs) in clinical and experimental exudates. They found an early coordinate appearance of LTs and PGs with polymorphonuclear neutrophil (PMNs) recruitment followed by the biosynthesis of lipoxins, concurrent with spontaneous resolution. In addition, human peripheral blood PMNs exposed to PGE₂ (as in exudates) switched eicosanoid biosynthesis from predominantly LTB₄ and 5-lipoxygenase (5-LO)–initiated pathways to LXA₄, a 15-LO product that 'stopped' PMN infiltration (Nat Immunol 2001, 2:612-619).

These results indicate that functionally distinct lipid-mediator...