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Tumoricidal activation of murine resident peritoneal macrophages by interleukin 2 and tumor necrosis factor alpha
S Verstovsek1, D Maccubbin, M J Ehrke
1Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, New York 14263.
Abstract:
The capacity of recombinant human interleukin 2 (rH-IL2), alone or in combination with recombinant tumor necrosis factor (r-TNF alpha), to activate murine resident peritoneal macrophages to a tumoricidal state was examined. Resident peritoneal exudate cells from C57BL/6 mice were cultured for 18 h with activating agents and washed and the adherent cells (macrophages) were assessed for cytolytic activity against radiolabeled target tumor cells (EL4, P815). Under these conditions, rH-IL2 alone activated macrophages to a tumoricidal state in a concentration dependent fashion. Neither murine nor human r-TNF alpha alone had any activating effect but, when combined with rH-IL2, further stimulated rH-IL2-inducible responses. Using polymyxin B, it was shown that macrophage activation was not due to an inadvertent lipopolysaccharide contamination of the r-TNF alpha or rH-IL2 preparations. It was also unlikely that target cell lysis was a direct result of increased TNF alpha production by rH-IL2 stimulated macrophages since P815 is totally resistant to lysis by r-TNF alpha. Although the lytic effector function was mediated by adherent cells, nonadherent peritoneal exudate cells were required for activation to occur. Furthermore, antisera against murine gamma-interferon, when added to activation cultures, reduced the level of cytolytic activity which developed. These data suggest that rH-IL2-induced peritoneal macrophage activation requires stimulation of nonadherent cells and is dependent upon gamma-interferon mediated mechanisms.
Insights
Recombinant human interleukin 2 (rH-IL2) activates mouse macrophages to kill tumor cells. This activation requires gamma-interferon and is enhanced by recombinant tumor necrosis factor alpha (r-TNF alpha).
Area of Science:
- Immunology
- Cell Biology
- Cancer Research
Background:
- Macrophages are key immune cells involved in tumor surveillance.
- Interleukin-2 (IL-2) and Tumor Necrosis Factor alpha (TNF alpha) are cytokines with immunomodulatory properties.
- Understanding macrophage activation is crucial for developing effective cancer immunotherapies.
Purpose of the Study:
- To investigate the ability of recombinant human interleukin 2 (rH-IL2) to activate murine peritoneal macrophages.
- To determine the effect of combining rH-IL2 with recombinant tumor necrosis factor alpha (r-TNF alpha) on macrophage activation.
- To elucidate the mechanisms underlying rH-IL2-mediated macrophage activation.
Main Methods:
- Murine resident peritoneal exudate cells were cultured with rH-IL2 and/or r-TNF alpha.
- Adherent macrophages were assessed for cytolytic activity against radiolabeled tumor cells (EL4, P815).
- Experiments included polymyxin B to rule out lipopolysaccharide contamination and anti-gamma-interferon antisera to assess its role.
Main Results:
- rH-IL2 alone activated macrophages to a tumoricidal state in a concentration-dependent manner.
- r-TNF alpha alone showed no activating effect but enhanced rH-IL2-induced responses when combined.
- Macrophage activation required nonadherent cells and was dependent on gamma-interferon, as indicated by reduced activity with anti-gamma-interferon antisera.
Conclusions:
- Recombinant human interleukin 2 effectively induces tumoricidal activity in murine macrophages.
- The activation process is potentiated by recombinant tumor necrosis factor alpha.
- rH-IL2-induced macrophage activation relies on gamma-interferon and involves nonadherent accessory cells.