Objective: To investigate the expression of the granulocyte-macrophage colony-stimulating factor (GM-CSF) and GM-CSF/IL-3/IL-5 receptor common beta chain (beta c receptor) in an adult patient with idiopathic pulmonary alveolar proteinosis (PAP), so as to demonstrate the possible association of the GM-CSF and beta c receptor with the pathogenesis of human PAP.
Methods: The GM-CSF levels were measured with a commercial ELISA kit (sensitivity 5 pg/ml) and the beta c receptor expression on the cell surface was detected by flow cytometry analysis. Reverse transcription polymerase chain reaction (RT-PCR) analysis was employed to detect the expression of the GM-CSF mRNA and the beta c receptor mRNA in peripheral blood mononuclear cells and alveolar macrophages. The entire coding regions of the GM-CSF cDNA and the beta c receptor cDNA were sequenced by the Sanger dideoxy-mediated chain termination method to detect possible mutations.
Results: The patient with PAP failed to release the GM-CSF protein either from circulating mononuclear cells or from alveolar macrophages. The expression of the GM-CSF mRNA was normal after the stimulation of lipopolysaccharide, whereas a point mutation at position 382 of the GM-CSF cDNA from "T" to "C" was revealed by cDNA sequencing, which caused a change in amino acid 117 of the protein from isoleucine to threonine. The beta c receptor expression on the cell surface was normal, and the beta c receptor mRNA expression and the sequence of the entire coding region of the beta c receptor were also normal.
Conclusions: The decreased GM-CSF production is associated with the pathogenesis of human PAP. A point mutation of the GM-CSF cDNA may contribute to the decreased GM-CSF production in our adult PAP patient. The mutation of the beta c receptor in some of paediatric patients with PAP may not be a common problem in adult patients.