Idiopathic pulmonary alveolar proteionsis (iPAP) is regarded as an autoimmune disease since anti-GM-CSF antibodies could be detected in blood and bronchoalveolar lavage fluid (BALF) of the patients. However, inflammation, the cardinal feature of autoimmune disease, is rarely demonstrated in lung parenchyma of the patients with iPAP. In this study, we measured inflammatory markers and compared the differences between patients with iPAP and inflammatory lung diseases.
Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, surfactant protein D (SP-D) and KL-6 were measured in BALF using enzyme-linked immunosorbent assays in 12 iPAP, 13 idiopathic pulmonary fibrosis (IPF), and 17 patients with connective tissue disease (CVD), and 17 controls without lung diseases.
Compared with controls, iPAP patients had higher values of TNF-α, IL-6, IL-8, SP-D and KL-6 in BALF. The patients with iPAP had significantly higher levels of BALF TNF-α, SP-D and KL-6 than did those with IPF and CVD. BALF values of IL-8 were comparable between the patients with iPAP and IPF, but significantly higher in patients with iPAP than in those with CVD. In iPAP patients, the levels of BALF IL-8 were highly correlated with the values of serum LDH; however, the levels of BALF KL-6 were negatively correlated with the value of PaO2.
Increased inflammatory cytokines, chemokines and markers of lung injury in BALF of the patients with iPAP highly suggested that inflammation of lung parenchyma might occur in iPAP. The reasons why inflammation of the lung has not yet been demonstrated in iPAP remain unknown. Further studies are needed to verify the issues.
Lung inflammation may play a relevant role in pathogenesis of iPAP.
Fang-Chi Lin, None.