Depletion of CD4+ CD25+ regulatory cells augments the generation of specific immune T cells in tumor-draining lymph nodes.
Recent studies have identified a unique population of CD4+CD25+ regulatory T cells that is crucial for the prevention of spontaneous autoimmune diseases. Further studies demonstrated that depletion of CD4+CD25+ T cells enhances immune responses to nonself antigens. Because immune responses to malignant tumors are weak and ineffective, depletion of regulatory T cells has been reported to result in tumor regression. In the current study, using the weakly immunogenic MCA205 sarcoma and the poorly immunogenic B16/BL6/D5 (D5) melanoma, depletion of CD4+CD25+ T cells by the administration of anti-CD25 monoclonal antibodies (mAb), PC61 induced some tumor growth retardation, but all mice eventually succumbed to tumors. In our laboratory, immunotherapy by the transfer of tumor-immune T cells has demonstrated potent antitumor effects. A reliable source of tumor-reactive T cells has been lymph nodes (LN) draining progressive tumors. Therapeutic effector T cells can be generated by in vitro activation of draining LN cells with anti-CD3 mAb followed by culture in interleukin-2. In this system, PC61 mAb depletion of CD4+CD25+ T cells before or on day 8 of tumor growth resulted in increased sensitization in the draining LN. The therapeutic efficacy of activated tumor-draining LN cells from mAb depleted mice increased approximately three fold while maintaining specificity when tested in adoptive immunotherapy of established pulmonary metastases. Specific interferon-gamma secretion by LN T cells from mice treated with PC61 mAb 1 day before tumor inoculation increased significantly. However, this increase was not demonstrated with LN T cells from mice treated on day 8 despite their enhanced therapeutic reactivities. Our results indicate that although the antitumor immunity enhanced by the depletion of CD4+CD25+ T cells is insufficient to eradicate tumors, it augments the sensitization of immune T cells in the draining LN, thus, facilitating adoptive immunotherapy.
Tanaka
Hiroshi
H
Center for Surgery Research/FF50, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, U.S.A.
Tanaka
Junta
J
Kjaergaard
Jørgen
J
Shu
Suyu
S
D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D015704:CD4 Antigens / Q000032:analysis / Q000502:physiology*; D005260:Female; D008198:Lymph Nodes / Q000276:immunology*; D008212:Lymphocyte Depletion; D051379:Mice; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental / Q000276:immunology* / Q000628:therapy; D015375:Receptors, Interleukin-2 / Q000032:analysis / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology*
D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D015375:Receptors, Interleukin-2