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In vitro activation of mouse macrophages by rat lymphocyte mediators
Abstract:
Macrophage-activating factors (MAF)3 were released by presensitized rat lymphocytes stimulated in vitro with the appropriate antigens. Different supernatants of presensitized rat lymphocytes specifically stimulated in vitro with several different mouse, dog, and rat tumor or normal cells were capable of rendering normal rat and mouse macrophages nonspecifically cytotoxic in vitro to their respective syngeneic tumor cells. The release of active mediators by rat lymphocytes sensitized in vivo was dependent upon immunologically specific recognition of an antigen in vitro. When rat lymphocytes were incubated in vitro with antigens unrelated to the in vivo sensitizing antigens, no release of MAF occurred. Once rat MAF was released, it activated both syngeneic (rat) and xenogeneic (mouse) macrophages to kill tumor cells in vitro. These activated marcophages destroyed all syngeneic tumor targets. Such cytotoxicity was obtained even when the cells used to elicit release of MAF were totally unrelated to the target tumor cells. The data thus demonstrated that MAF can cross strain and even species specificities and can activate macrophages to kill tumors in a nonspecific manner. The cytotoxicity mediated by in vitro activated mouse macrophages decreased with time once the macrophages were removed from MAF; and by 7 days postactivation, the macrophages were not cytotoxic. However, when incubated again with MAF, significant reactivation was observed. This suggested that activation of macrophages in vivo may be a continuous process of lymphocyte-macrophage interaction.
Insights
Rat lymphocytes release macrophage-activating factors (MAF) that nonspecifically activate macrophages to kill tumor cells across species. MAF activation is reversible, suggesting continuous lymphocyte-macrophage interaction is needed in vivo.
Area of Science:
- Immunology
- Cell Biology
- Cancer Research
Background:
- Macrophage-activating factors (MAF) are crucial mediators in immune responses.
- Understanding MAF's role in tumor cell destruction is vital for immunotherapy.
- Lymphocyte-macrophage interactions are key to immune surveillance.
Purpose of the Study:
- To investigate the antigen specificity and cross-species activity of MAF.
- To determine the duration and reversibility of macrophage activation by MAF.
- To explore the implications of MAF activity for in vivo immune responses.
Main Methods:
- In vitro stimulation of presensitized rat lymphocytes with specific antigens.
- Collection and application of lymphocyte supernatants (containing MAF) to normal rat and mouse macrophages.
- Assessment of macrophage cytotoxicity against syngeneic tumor cells.
- Evaluation of MAF-induced cytotoxicity over time and after re-exposure.
Main Results:
- MAF released by lymphocytes specifically recognize antigens and activate macrophages.
- Activated macrophages exhibit non-specific cytotoxicity against tumor cells, even across species.
- Macrophage activation by MAF is transient and reversible, requiring continuous exposure for sustained cytotoxicity.
- MAF can cross strain and species specificities.
Conclusions:
- MAF plays a significant role in non-specific tumor cell killing by macrophages.
- The transient nature of MAF-induced activation suggests a dynamic in vivo process.
- Lymphocyte-macrophage interactions are essential for sustained anti-tumor immunity.