Colony assay using collagen gel: a better technique for studying the cell morphology of colonies

Collagen gel was used as a substance for the assay of human granulocyte-macrophage colony-forming units (CFUc). The number of colonies formed in collagen gel was consistently higher than that in a conventional soft-agar system. In six out of eight experiments, the difference was statistically significant. Whole permanent preparations of the plates were made easily and were stained by Giemsa solution with minimum background staining. Preservation of cellular morphology in the preparations was excellent, and neutrophil, macrophage, and eosinophil colonies could be differentiated by their nuclear shape, cytoplasmic color, and specific granules.