NASAL NEUTROPHILIA AND RELEASE OF MYELOPEROXIDASE INDUCED BY NASAL CHALLENGE WITH PLATELET-ACTIVATING-FACTOR - DIFFERENT DEGREES OF RESPONSIVENESS IN ATOPIC AND NONATOPIC SUBJECTS

Background: Nasal challenge with platelet activating factor (PAF) is a ble to induce local neutrophilia, with a different degree of responsiv eness in atopic subjects and in nonatopic subjects. We investigated wh ether nasal accumulation of neutrophils induced by PAF is accompanied by the release of neutrophil-derived mediators. Methods: Nasal lavages were performed before and after challenge with PAF (500 nmol), lyso-P AF (500 nmol), and saline solution in 10 patients with allergic rhinit is and 10 normal subjects to evaluate changes in neutrophil counts and the release of myeloperoxidase (MPO) and immunoreactive leukotriene B -4. Results: PAF caused neutrophilia, which appeared after 30 minutes in atopic subjects and after 3 hours in nonatopic subjects. Furthermor e, when compared with saline insufflation, PAF caused a significant re lease of MPO in the nasal lavage fluids collected 30 minutes, 3 hours, and 24 hours after challenge in atopic subjects and 3 hours after cha llenge in nonatopic subjects, with higher values in the former than in the latter. Neutrophil counts correlated with MPO levels in the nasal lavages collected after PAF challenge. A lower degree of neutrophilia was found 3 hours after stimulation with lyso-PAF in both groups of s ubjects, with a marginal release of MPO in atopic subjects only. No si gnificant increase of immunoreactive leukotriene B-4 levels in nasal l avages was found after challenge with either PAF or lyso-PAF. Conclusi on: These results indicate that PAF-induced neutrophilia in the nose i s accompanied by the release of MPO, which appears earlier and is more marked in atopic subjects than in nonatopic subjects.