Human surfactant protein a suppresses T cell-dependent inflammation and attenuates the manifestations of idiopathic pneumonia syndrome in mice

We have previously shown an association between growth factor-induced upregulation of surfactant protein (SP)-A and suppression of alveolar inflammation in our murine model of donor T cell-dependent lung dysfunction after bone-marrow transplantation, referred to as idiopathic pneumonia syndrome (IPS). We hypothesized that SP-A protects the lung in vivo from IPS injury by downregulation of alveolar inflammation. Human SP-A (100 μg), purified by n-butanol extraction or preparative isoelectric focusing, was transtracheally instilled on Day 4 after BMT during a time of in vivo donor T-cell activation. At 48 h after treatment, immunohistochemical staining of lung sections showed that SP-A did not alter T cell -dependent cellular infiltration. However, macrophages from SP-A-instilled mice were less injured and spontaneously produced less tumor necrosis factor-α than did cells from buffer -instilled mice. Although exogenous SP-A did not significantly alter bronchoalveolar lavage fluid (BALF) high levels of total protein (TP), an inverse correlation between BALF SP-A and TP concentrations (r = -0.65; P = 0.02) was observed in SP -A-treated but not in buffer-instilled mice. The only difference between the effects of the two sources of SP-A was that butanol -extracted SP-A, but not isoelectric focusing-purified SP -A, suppressed the interferon-γ/nitric oxide pathway. We conclude that SP-A downregulates T cell-dependent alveolar inflammation by multiple pathways leading to decreased IPS injury.