Immunoregulatory role of secretory leukocyte protease inhibitor in allergic asthma

Results Allergic SLPI transgenic mice showed a significant decrease in airway resistance compared to wild-type mice (6.3 ± 1.1 vs. 8.0 ± 2.1 cm H20 × s/ml, p < 0.001), the same effect was observed with inflammatory cell infiltration, eosinophil percentage (24 ± 1.1% vs. 29 ± 2.3%, p < 0.001), goblet cells (6 ± 1.4 vs. 36 ± 4.0%, p < 0.001) in the lungs and IgE levels (2014.1 ± 309.2 vs. 4173.2 ± 685.6 ng/ml, p < 0.001) in plasma. Allergic SLPI knock-out mice displayed significantly higher values compared to wild-type mice. They include lung resistance (8.6 ± 2.7 vs. 6.6 ± 0.5 cm H20*s/ml, p < 0.001), inflammatory cell influx, eosinophils (36.0 ± 2.7 vs. 29.0 ± 1.5%, p < 0.001), goblet cells (40 ± 4.1 vs. 30 ± 1.4%, p < 0.001), cytokine levels in the lungs (p < 0.05) and plasma IgE levels (3598 ± 204.7 vs. 2763 ± 220.3 ng/ml, p < 0.001). Expression of SLPI decreased inflammation in the lungs, plasma IgE levels, and lung resistance, whereas the ablation of SLPI has the opposite effect. Treatment with resiquimod improved airway resistance and inflammation of the lungs in SLPI knockout and wild type, demonstrating that its effect is independent of the expression of SLPI. Conclusions SLPI plays an immunoregulatory role in the respiratory tract by reducing the inflammatory process and by improving lung physiology in a murine model of acute allergic asthma.