Macrophage colony-stimulating factor (CSF-1) gene expression in human T-lymphocyte clones

Macrophage colony stimulating factor (CSF-1) is one of several cytokines that control the differentiation, survival, and proliferation of monocytes and macrophages. A set of 11 human T-cell clones, chosen for their phenotypic diversity, were tested for their ability to express CSF-1 mRNA. After 5 hours of stimulation with phorbol myristate acetate (PMA) + calcium ionophore (Cal), all T-cell clones expressed a major 4-kb transcript, a less abundant 2-kb transcript, and several other minor species. This pattern of expression is typical for CSF-1 mRNAs. Furthermore, of the two alloreactive T-cell clones analyzed, only one showed a definitive message for CSF-1 on specific antigenic stimulation, but with delayed kinetics and less efficiency. Both conditions of stimulation induced the release of CSF-1 protein by T cells in the culture medium. Together, these findings demonstrate for the first time that normal T cells are able to produce CSF-1, previous reports being limited to two cases of tumoral cells of the T-cell lineage.