GM-1, a clone of the monoblastic phagocyte U937 that expresses a large respiratory burst capacity upon activation with interferon-gamma.

The human cell line U937 was cloned and screened for the responsiveness to interferon-gamma (INF-gamma). The selected subclone, named GM-1, expressed a high density of IFN-gamma receptors and showed HLA typing similar to that of the parental line but was devoid of the Y chromosome. GM-1 cells display a promyeloid phenotype as revealed by flow cytometry using a panel of murine antibodies. Following treatment with IFN-gamma GM-1 cells differentiated to a more mature monocyte stage and acquired the capacity to mount a respiratory burst. After treatment with differentiation promotors, such as phorbol 12-myristate 13-acetate (PMA), dimethyl sulfoxide (DMSO), and retinoic acid, GM-1 showed a more limited respiratory burst capacity. Superoxide release in IFN-gamma-activated cells was stimulated with f-Met-Leu-Phe, C5a, or PMA. The development of the respiratory burst capacity was accompanied with the expression of cytochrome b558, a component of the phagocyte NADPH-oxidase. GM-1 cells are useful for the study of the effects of IFN-gamma on the respiratory burst. They are more sensitive and yield a more homogenous response to IFN-gamma than U937 cells. The phenotype of GM-1 cells was stable for more than 5 years.