Leukocyte‐deactivating factor from macrophages: Partial purification and biochemical characterization. A novel cytokine

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Abstract
A deactivating factor (MDF) is released from granuloma‐like lesions of mice (giant and epithelioid macrophages) to the surrounding medium. Test cells incubated in the presence of MDF display dramatic inhibition of superoxide anion (O2−) release when stimulated. This failure to manifest O2 release is observed whether PMA, all‐transretinal, or fMet‐Leu‐Phe is the stimulating agent. MDF acts on different cell types from different species; mouse macrophages as well as guinea pig, human, and mouse neutrophils. Such results suggest that it is a universal regulatory cytokine with high affinity for phagocytic lineages. The factor was subjected to various purification methods: ultrafiltration, gel chromatography, and reversed phase HPLC. A crude preparation that resulted from conditioning of medium by old macrophages (MCM) shows two peaks of activity when subjected to gel filtration. These correspond to molecular weights for the active principle of 3 and 11 kD. When the factor was obtained by extraction of the same cells after washing and sonication. Only the former peak was seen. Fractions corresponding to a MW of 3 kD from several preparations were combined and subjected to HPLC. MDF activity then appeared in a single fraction. MDF is thus putatively a modulator of the cidal activity of phagocytic cells that utilize release of reactive oxygen species for cytocidal activity.