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Promonocytes have the functional characteristics of natural killer cells
Abstract:
Promonocytes isolated from a 5-day-old L-fibroblast-conditioned liquid bone marrow culture show strong NK cell cytotoxicity. They kill YAC target cells in a short-term 125IUDR-release assay whereas P815 targets are unaffected. This NK-like cytotoxicity is enhanced in the presence of interferon preparations. Morphologically, these promonocytes resemble a medium size lymphocyte with a high nucleus to cytoplasma ratio, they are nonadherent, nonphagocytic, and negative in nonspecific esterase staining. Promonocytes are precursor cells from macrophages, which have not yet developed the typical macrophage criteria. Within 24 to 48 hr they mature to adherent macrophages. We have shown previously, that the same promonocytes have the capacity to perform K cell killing of antibody-coated tumor target cells. The cytotoxic effector functions of promonocytes are abolished when the cells are treated with the alloantimacrophage serum Mphi 1.2 plus rabbit C. The relationship or similarity between K cells, NK cells and promonocytes is discussed.
Insights
Promonocytes, macrophage precursors, exhibit natural killer (NK) cell-like cytotoxicity against specific targets. This activity is enhanced by interferon and is distinct from typical macrophage functions.
Area of Science:
- Immunology
- Cell Biology
Background:
- Promonocytes are precursor cells to macrophages.
- Their functional characteristics, particularly cytotoxic activity, are not fully elucidated.
Purpose of the Study:
- To investigate the cytotoxic potential of promonocytes.
- To characterize the nature of their effector functions and compare them to known cytotoxic cells.
Main Methods:
- Isolation of promonocytes from bone marrow cultures.
- Cytotoxicity assays using YAC and P815 target cells.
- Assessment of NK-like cytotoxicity enhancement with interferon.
- Morphological and functional characterization (adherence, phagocytosis, esterase staining).
- Functional blockade using anti-macrophage serum and complement.
Main Results:
- Promonocytes demonstrate significant natural killer (NK) cell-like cytotoxicity against YAC targets but not P815 targets.
- This NK-like cytotoxicity is augmented by interferon preparations.
- Morphologically, promonocytes resemble lymphocytes and lack typical macrophage features.
- Cytotoxic functions are abrogated by anti-macrophage serum treatment, suggesting a macrophage-related lineage.
Conclusions:
- Promonocytes possess potent NK cell-like cytotoxic effector functions.
- These functions are distinct from mature macrophage activities and can be modulated by interferon.
- The findings contribute to understanding the early differentiation stages and functional plasticity of the monocyte-macrophage lineage.