Abstract:
The increase of alveolar macrophages in jaagsiekte sheep lungs is not caused by excessive surfactant production but is due to a chemotactic factor secreted by the tumour cells. This factor has a molecular mass in the region of 13 kilodaltons, is stable at 56 °C but labile at 100 °C and, being sensitive to proteases, indicates that it is a small protein molecule.
