Allergen‐induced bronchial inflammation is associated with decreased levels of surfactant proteins A and D in a murine model of asthma

Background Increasing evidence suggests that pulmonary surfactant protein A (SP‐A) and D (SP‐D) participate in the lung defence against pathogens. However, the role of surfactant proteins in the pathogenesis of allergen‐induced airway inflammation has not been elucidated. In this study we examined the levels and distributions of SP‐A and SP‐D in a dust mite ( Dermatophagoides pteronyssinus, Der p) allergen‐induced murine model of asthma. Methods The concentration of SP‐A and SP‐D in the bronchoalveolar lavage fluid (BALF) and the distribution of surfactant proteins in the lung were assayed by ELISA and immunohistochemistry methods, respectively. The effect of surfactant proteins on allergen‐induced pulmonary lymphocyte proliferation was also studied. Results We demonstrated that there were marked reductions of SP‐A and SP‐D levels in the BALF of Der p‐sensitized BALB/c mice at 48–72 h after allergen challenge (AC). Both purified SP‐A and SP‐D were able to suppress, in a dose dependent manner, Der p‐stimulated intrapulmonary lymphocyte proliferation of naïve mice with saline or allergen challenge, or of Der p‐sensitized mice with saline challenge. On the contrary, this suppressive effect was mild (< 9%) on lymphocytes from sensitized mice after AC. Conclusion These results indicated the involvement of pulmonary surfactant proteins in the allergic bronchial inflammation of sensitized mice.