PI3 and infection: Figures 2a and 2b show the increased infection efficiency of alveolar macrophages by the incorporation of Ad-GFP in a calcium phosphate precipitate. The use of calcium phosphate increased both the number of macrophages infected and the intensity of fluorescence per infected cell. Similarly, figure 2c shows that the infection of alveolar macrophages with Ad-o-elafin-FLAG in conjunction with calcium phosphate increases the secretion of ovine elafin.