Inhibition of eosinophilic inflammation in allergen-challenged, IL-1 receptor type 1-deficient mice is associated with reduced eosinophil rolling and adhesion on vascular endothelium

To determine the relative in vivo importance of IL-1 release after allergen challenge to the subsequent endothelial adhesion and recruitment of eosinophils, the authors used ovalbumin sensitization and inhalation challenge to induce airway eosinophilia in IL-1 receptor type 1-deficient and control wild-type mice. Broncho-alveolar lavage (BAL) eosinophil recruitment in IL-1 receptor type 1-deficient mice challenged with ovalbumin (24.3% ± 6.3% BAL eosinophils) was significantly reduced compared with wild- type mice (63.7% ± 2.5% BAL eosinophils). To determine whether the inhibition of eosinophil adhesion to vascular endothelium contributed to the inhibition of eosinophil recruitment in IL-1 receptor type 1-deficient mice, the authors used intravital microscopy to visualize the rolling and firm adhesion of fluorescence-labeled mouse eosinophils in the microvasculature of the allergen-challenged mouse mesentery. Eosinophil rolling, eosinophil firm adhesion to endothelium, and transmigration across endothelium (peritoneal eosinophils) were significantly inhibited in allergen-challenged IL-1 receptor type 1-deficient mice compared with wild-type mice. Overall, these studies demonstrate that cytokines such as IL-1, released after allergen challenge, are important in the induction of endothelial cell adhesiveness, a prerequisite for the recruitment of circulating eosinophils.