Detection of secreted IGF-E5 from stable CHO transfectants by FLSSM. A, C and E: transmitted light images. B, D and F: green fluorescence at 510 nm from anti-His Tag/FITC antibody present in semi-solid medium; fluorescent dots formed by reaction of anti-His Tag/FITC with secreted IGF-E5 bearing His Tag moiety. A and B: longer exposure from single cell showing a cloud of fluorescent dots. C and D: positive CHO-IGF-E5 colony: signal is weak, but sufficient for detection of high producing cells. E and F: negative control; CHO cells secreting an unrelated product do not react with anti-His Tag antibody.