PLUNC is a secreted product of neutrophil granules.

Airway epithelia and neutrophils are frequently recruited to release host defense factors in response to a variety of pulmonary pathogens. One abundant product of airway epithelia is palate, lung, nasal epithelium clone (PLUNC), a proposed innate immune protein expressed in submucosal glands and surface airway epithelia. In this study, we report the expression of PLUNC in human neu- trophils, a previously unrecognized source of this protein. Immunoblots performed on polymorpho- nuclear cell (PMN) lysates and PMN subcellular fractions indicated that PLUNC was present in the specific granules of the neutrophil. Furthermore, secretion assays demonstrated that PLUNC protein was released by neutrophils upon stimulation with secretogogues, including formyl methionyl leucyl phenylalanine and the calcium ionophore A23187. Although recombinant PLUNC protein failed to exhibit antibacterial activity in our studies, its stor- age and secretion by a professional phagocytic cell support the hypothesis that PLUNC participates in an aspect of the inflammatory response that con- tributes to host defense. These studies suggest that PLUNC expression is less restricted than previ- ously believed, and highlight new avenues of re- search for the study of PLUNC function. J. Leukoc. Biol. 83: 1201-1206; 2008.