Neisseria meningitidis pili induce type‐IIA phospholipase A2 expression in alveolar macrophages

Induction of type‐IIA secreted phospholipase A2 (sPLA2‐IIA) expression by bacterial components other than lipopolysaccharide has not been previously investigated. Here, we show that exposure of alveolar macrophages (AM) to Neisseria meningitidis or its lipooligosaccharide (LOS) induced sPLA2‐IIA synthesis. However, N. meningitidis mutant devoid of LOS did not abolish this effect. In addition, a pili‐defective mutant exhibited significantly lower capacity to stimulate sPLA2‐IIA synthesis than the wild‐type strain. Moreover, pili isolated from a LOS‐defective strain induced sPLA2‐IIA expression and nuclear factor kappa B (NF‐κB) activation. These data suggest that pili are potent inducers of sPLA2‐IIA expression by AM, through a NF‐κB‐dependent process.