title: CD40 ligation in vivo can induce T cell independent antitumor effects even against immunogenic tumors.
abstract: Antitumor effects of CD40 ligation appear to involve distinct antitumor effector cells in different experimental models. In this study, we tested whether T cells were required for antitumor effects of agonistic anti-CD40 mAb (alphaCD40) against immunogenic versus poorly immunogenic tumors. Treatment of mice bearing poorly immunogenic B16 melanoma and its more immunogenic variant, B16-hsp72.1, with alphaCD40 resulted in a similar level of tumor growth suppression. Depletion of T cells did not reduce the antitumor effects in these 2 tumor models. To generate antitumor T cell responses, C57BL/6 mice were immunized with irradiated B16-hsp72.1. Treatment of these vaccinated mice challenged with a high dose of B16-hsp72.1 tumor cells with alphaCD40 induced tumor growth suppression, which was reduced by T-cell depletion, demonstrating that T cells were involved in the antitumor effect of alphaCD40. However, immunized mice depleted of T cells and treated with alphaCD40 were still able to suppress tumor growth as compared to tumor growth in immunized, T cell-depleted mice not treated with alphaCD40, suggesting that T cells were not required for the antitumor effect of alphaCD40. To confirm a lack of correlation between tumor immunogenicity and T-cell requirement in antitumor effects of CD40 ligation, we found that alphaCD40 induced tumor growth suppression in nude and SCID/beige mice bearing highly immunogenic tumors such as Meth A sarcoma, suggesting that macrophages may play a role. Indeed, both poorly immunogenic and highly immunogenic tumors were sensitive to in vitro growth inhibition by macrophages from alphaCD40-treated mice. Taken together, our results indicate that antitumor effects induced by alphaCD40, even against immunogenic tumors, can be observed in the absence of T cells and may involve macrophages.
authors.affiliation: The Department of Human Oncology, University of Wisconsin, K4/413 Clinical Science Center, 600 Highland Avenue, Madison, WI 53792, USA. rakhmil@humonc.wisc.edu
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Rakhmilevich
authors.forename: Ilia N
authors.initials: IN
authors.lastname: Buhtoiarov
authors.forename: Miroslav
authors.initials: M
authors.lastname: Malkovsky
authors.forename: Paul M
authors.initials: PM
authors.lastname: Sondel
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology / Q000627:therapeutic use*; D019013:CD40 Antigens / Q000276:immunology; D019496:Cancer Vaccines / Q000276:immunology / Q000494:pharmacology / Q000627:therapeutic use; D002292:Carcinoma, Renal Cell / Q000276:immunology / Q000628:therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D005260:Female; D007167:Immunotherapy; D007680:Kidney Neoplasms / Q000276:immunology / Q000628:therapy*; D007940:Leukemia L5178 / Q000276:immunology / Q000628:therapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008819:Mice, Nude; D016513:Mice, SCID; D009368:Neoplasm Transplantation / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D019013:CD40 Antigens; D019496:Cancer Vaccines