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. How ever, the role of surfactant proteins in the pathogenesis of allergen-induc ed airway inflammation has not been elucidated. In this study we examined t he levels and distributions of SP-A and SP-D in a dust mite (Dermatophagoid es pteronyssinus, Der p) allergen-induced murine model of asthma. Methods The concentration of SP-A and SP-D in the bronchoalveolar lavage fl uid (BALF) and the distribution of surfactant proteins in the lung were ass ayed 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 allerge n challenge (AC). Both purified SP-A and SP-D were able to suppress, in a d ose dependent manner, Der p-stimulated intrapulmonary lymphocyte proliferat ion of naive mice with saline or allergen challenge, or of Der p-sensitized mice with saline challenge. On the contrary, this suppressive effect was m ild (< 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.