CSF2 and autoimmune pulmonary alveolar proteinosis: Prior studies of Lin et al. also revealed that, whereas the level of serum anti-GM-CSF Abs did not correlate with severity of iPAP, the level of anti-GM-CSF Abs in BAL fluid directly correlated with disease severity markers such as serum LDH, PaO2, D(A-a)O2 and DLCO, further predicting the need for subsequent therapeutic lavage, which implies the interrelation between degree of alveolar capillary damage and severity of iPAP [19, 21].