Surfactant protein A exhibits inhibitory effect on eosinophils IL-8 production

Eosinophils are believed to be one of the important sources of cytokines such as IL-8 at the site of allergic inflammation. It has been demonstrated that pulmonary surfactant protein A (SP-A) plays a potential role in modifying inflammation and the immune function. To verify the regulating effect of SP-A on eosinophil cytokine generation, we studied the effect of SP-A by determining of IL-8 production and expression stimulated with sIgA or PMA. SP-A purified from surfactant recovered from patients with alveolar proteinosis was added to eosinophils isolated by the negative selection method with immunomagnetic beads, and cultured for 24 h. The concentrations of IL-8 in the cell-free supernatants and cell lysates were then measured by ELISA. We also used a semiquantitative reverse transcriptase-polymerase chain reaction assay to detect the effect of SP-A on IL-8 mRNA expression. SP-A inhibited the secretion of IL-8 in a dose-dependent fashion. Suppression of IL-8 production by SP-A was significantly inhibited by SP-A antibody (PE10). SP-A also attenuated expression of IL-8 mRNA in eosinophils. These results indicate that SP-A might have the potential role to modify allergic inflammation by inhibiting IL-8 expression and production from eosinophils.