Characterization of cells cultured from early lactation milks.

Two major types of cells can be cultured from early lactation human milks: a colony-forming epithelial cell and an adherent nondividing cell referred to as a foam cell. The epithelial cells show a positive reaction with a specific antiserum reactive against membrane components of the milk fat globule, whereas the foam cells do not. The nondividing foam cells are phagocytic and can be killed by silica particles; they produce lysozyme, are resistant to trypsinization, and have Fc receptors. These properties, together with the lack of reaction with antiserum to the milk fat globule membrane, suggest that the foam cells are not terminally differentiated epithelial cells, but tissue macrophages.