Temporal relationships between leukocytes, IL-5 and IL-8 in guinea pig lungs, plasma cortisol and airway function...

The aim was to determine the time courses for the changes in airway function, airway reactivity, influx of inflammatory cells and levels of the pro-inflammatory cytokines, interleukin (IL)-5 and IL-8 in bronchoalveolar lavage fluid (BALF), and the plasma levels of cortisol and ACTH after antigen challenge to determine whether a temporal link could be established between these events.

Airway function was measured as specific airway conductance (sGsw) in conscious ovalbumin (OvA)-sensitized guinea pigs using whole body plethysmography at intervals after an inhalation challenge with ovalbumin (0.5% for 10 min). Airway responses to the inhaled spasmogen, U46619 (30 ng/ml, 60 s), were measured at 3, 6 and 24 h after challenge. In separate animals, bronchoalveolar lavage fluid (BALF) was obtained after anaesthetic overdose either before challenge or at 1, 3, 6, 12, or 24 h after OvA challenge. Total and differential cell counts of eosinophils and neutrophils were performed on BALF and levels of IL-5 and IL-8 determined by scintillation proximity assays and ELISA, respectively. Plasma cortisol and ACTH levels were determined by RIA kits in blood removed by cardiac puncture at intervals after challenge.

An early phase bronchoconstriction occurred which resolved by 3 h and was followed by a late phase between 17 and 24 h. Airway hyperresponsiveness to inhaled U46619, was evident at 3, 6 and 24 h after antigen challenge. Increased IL-5[BALF] was observed by 60 min post challenge implicating a performed storage site. In contrast, IL-8[BALF] was not raised until 3 h post challenge. There was a significant infiltration of neutrophils and eosinophils by 3 and 6 h, respectively. IL-5[BALF] further increased up to 24 h, during the appearance of the late phase of bronchoconstriction and whilst eosinophilia was maximal. Plasma cortisol levels were increased 1 and 3 hours after antigen challenge, thereafter returning to baseline levels.

The hyperresponsiveness appears to be dissociated from the appearance of eosinophils in lavage fluid. The early appearance of IL-5, however, could be a trigger for the migration of eosinophils and development of hyper-responsiveness. The increased plasma cortisol levels occurring after antigen challenge were presumably due to the stress involved and these would be expected to exert an endogenous anti-inflammatory effect.