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Demonstration of a human lymphokine which renders macrophages cytotoxic
Abstract:
Incubation of human peritoneal macrophages with cell free supernatants of mixed human lymphocyte cultures (MLC) renders them cytotoxic to labelled target tumour cells. The factor responsible for this effect is found as early as the second day of MLC. The production of this factor in man does not seem to require previous sensitization. In contrast with observations in mice, we have not yet demonstrated in man any clear-cut difference between the macrophage cytotoxicity index observed with supernatants from normal MLC and from MLC between the donor and the recipient of a skin allograft. Human blood monocytes can also be rendered cytotoxic by MLC acellular supernatants, but their cytotoxicity is neither as consistent nor as strong as with macrophages. This human factor does not render mouse macrophages cytotoxic.
Insights
Human mixed lymphocyte cultures (MLC) produce a factor that makes macrophages cytotoxic to tumor cells. This immune factor appears early in MLC and doesn't require prior sensitization in humans.
Area of Science:
- Immunology
- Cell Biology
- Cancer Research
Background:
- Human peritoneal macrophages can be activated to kill target tumor cells.
- Mixed lymphocyte cultures (MLC) are a key model for studying immune cell interactions.
- Understanding immune cell activation is crucial for developing cancer therapies.
Purpose of the Study:
- To investigate the production and characteristics of a cytotoxic factor generated during human mixed lymphocyte cultures (MLC).
- To determine if this factor requires prior sensitization and if it differs in normal versus allograft-related MLC.
- To compare the cytotoxic effects on human macrophages and monocytes, and assess cross-species activity.
Main Methods:
- Incubation of human peritoneal macrophages with cell-free supernatants from human MLC.
- Assessing cytotoxicity against labeled target tumor cells.
- Comparing supernatants from normal MLC with those from MLC involving skin allograft donors and recipients.
- Testing the effect of human MLC supernatants on mouse macrophages.
Main Results:
- MLC supernatants induce cytotoxicity in human peritoneal macrophages against tumor cells.
- The cytotoxic factor is detectable by day two of MLC and its production does not appear to require prior sensitization.
- Human blood monocytes also exhibit MLC-induced cytotoxicity, though less consistently and potently than macrophages.
- The human factor does not activate mouse macrophages.
Conclusions:
- A soluble factor produced during human MLC can render macrophages cytotoxic to tumor cells, independent of prior sensitization.
- This phenomenon in humans differs from mouse models, particularly regarding allograft sensitization.
- Human monocytes can be activated but are less responsive than macrophages, and the factor is species-specific.