Release of granulocyte-macrophage colony-stimulating activity from human alveolar macrophages and its support of human myeloid blast cell proliferation.

The ability of human alveolar macrophages to support colony formation of precursor blast cells of the myeloid lineage was investigated. Myeloid blast cells were collected from patients with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and from the livers of fetuses aborted in the second trimester of gestation. It was found that the alveolar macrophages (AM) produced sufficient amount of colony-stimulating activity which culminated in the fourth week of in vitro cultivation. Conditioned media from AM supported the growth of multipotential blast cell colonies (GEMM-CFU) in AML and MDS, while in fetal hemopoiesis macrophage colonies preponderated. Preincubation with human interferon-alpha (IFN-alpha) can abrogate the production of the granulocyte-macrophage colony stimulating factor (GM-CSF) by AM. Media conditioned by AM were not able to compensate for cell-to-cell contact in long-term cultures of AML blast cells but CSFs released from AM in vivo can contribute to aggravation of the disease.