Quantification of mGM-CSF in lavage fluid after transfer of genetically modified AM to the lung. Alveolar macrophages were infected in vitro with AdmGM-CSF or AdNull at 100 moi for 90 minutes and washed, and 2 × 10⁵ AM were transplanted by the intratracheal route to the lungs of syngeneic mice. As a control, a parallel group of animals received 60 ng recombinant mGM-CSF (r-mGM-CSF). Quantification of mGM-CSF in lavage fluid was performed by ELISA 1 week after administration. The data are expressed as picograms of mGM-CSF in lavage fluid referenced to milligrams of total protein in the recovered fluid. The dashed line represents the lower limit of detection of the assay.