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Mechanisms of immunosuppression in tumor-bearing mice: a multifactorial analysis
Abstract:
Neoplastic growth results not only from the inherent proliferative potential of the neoplasm, but also from the neoplasm's ability to survive within a host whose immune responses may be activated to destroy it. It has been proposed that several mechanisms enable a neoplasm to outgrow the host. The present work describes a system for probing tumor-associated immunosuppression by utilization of the delayed hypersensitivity response to dinitrochlorobenzene (DNCB). Mice of the Balb/c and C3H/HeJ strains were sensitized with a subcutaneous injection of 2 mg DNCB followed 5-10 days later by the subcutaneous injection of a 0.05 mg challenge dose of DNCB in the hind footpad. The footpad response measured 24 hours after challenge is a delayed hypersensitivity reaction by virtue of the histology and kinetics of that response and because it is transferred by spleen cells but not by serum. DNCB sensitization is inhibited by spontaneous, chemical- and virus-induced syngeneic tumors in Balb/c and C3H/HeJ mice. Three mechanisms of immunosuppression are elucidated in the present experiments: (1) serum from tumor-bearing mice inhibits primary sensitization of normal mice to DNCB upon passive transfer; (2) spleen cells from tumor-bearing mice inhibit primary sensitization of normal mice to DNCB and appear to be macrophages in the C3H/HeJ system; and (3) an alteration of lymphocyte migration patterns exists in tumor-bearing mice that removes effector cells from the blood and prevents the initiation of a footpad response. The interrelationships of these three mechanisms are discussed. Correlations are also made with tumor-associated immunosuppression observed in cancer patients.
Insights
Tumors can suppress the immune system, hindering the body's ability to fight cancer. This study reveals three key mechanisms, including serum factors, spleen cell activity, and altered lymphocyte migration, contributing to tumor-associated immunosuppression.
Area of Science:
- Immunology
- Oncology
- Cellular Biology
Background:
- Neoplastic growth depends on tumor proliferation and evasion of host immune responses.
- Tumor-associated immunosuppression is a critical factor enabling cancer to outgrow the host.
- Understanding these immunosuppressive mechanisms is vital for developing effective cancer therapies.
Purpose of the Study:
- To investigate tumor-associated immunosuppression using a delayed hypersensitivity response model.
- To elucidate the specific mechanisms by which neoplasms inhibit immune responses in mice.
- To correlate findings in a murine model with immunosuppression observed in cancer patients.
Main Methods:
- Utilized the delayed hypersensitivity response to dinitrochlorobenzene (DNCB) in Balb/c and C3H/HeJ mice.
- Administered DNCB sensitization and challenge doses subcutaneously.
- Assessed the footpad response 24 hours post-challenge, analyzing histology, kinetics, and cell transfer (spleen cells vs. serum).
Main Results:
- Spontaneous, chemical-, and virus-induced syngeneic tumors inhibited DNCB sensitization in mice.
- Identified three immunosuppressive mechanisms: inhibitory serum factors, immunosuppressive spleen cells (macrophages in C3H/HeJ), and altered lymphocyte migration patterns.
- Demonstrated that tumor-bearing mice exhibit reduced effector cell circulation, preventing immune responses.
Conclusions:
- Tumor-associated immunosuppression involves multiple, interconnected mechanisms that impair the host's immune surveillance.
- The DNCB delayed hypersensitivity model effectively probes these immunosuppressive effects.
- Findings provide insights into cancer immune evasion strategies and potential therapeutic targets relevant to human cancer patients.