Serum surfactant protein D is elevated in allergic patients.

BACKGROUND: There is evidence that surfactant protein (SP)-D is important in the innate, as well as in the adaptive pulmonary immune response. Serum concentrations of SP-D have been proposed as parameter of the integrity of the blood-airspace barrier in interstitial lung diseases. We hypothesized that serum SP-D concentrations are affected in allergic patients and correlate with changes in allergic airway inflammation. OBJECTIVE: To determine levels of serum SP-D in allergic patients compared with non-allergic controls. Furthermore, to investigate associations between serum SP-D concentrations on the one hand and changes in commonly used markers of bronchial inflammation in allergic airways disease on the other hand. MATERIALS AND METHODS: Fifty allergic patients were studied and bronchial allergen challenge was used as a model to increase bronchial allergic inflammation in these patients. Serum SP-D concentrations, inflammatory parameters in induced sputum and bronchial hyper-responsiveness (BHR) were determined before and after allergen challenge. Twenty-five non-allergic volunteers served as controls. RESULTS: Baseline serum SP-D was significantly higher in allergic patients as compared with controls (mean serum SP-D concentration (95% confidence interval): 62.7 (55.5, 70.0) in allergic patients vs. 49.5 (36.7, 62.3) ng/mL in non-allergic controls, P=0.006). In addition, baseline serum SP-D appeared to be an independent predictor for the magnitude of the late asthmatic response after allergen challenge. Furthermore, serum SP-D was predictive for the sputum eosinophil cationic protein concentration after allergen challenge. CONCLUSION: We propose that serum SP-D concentrations are associated with allergic bronchial inflammation and may give additional information, beside BHR and sputum eosinophils, about the degree of bronchial inflammation in allergic patients.