title: Importance of tumor-specific cytotoxic CD8+ T-cells in eradication of a large subcutaneous MOPC-315 tumor following low-dose melphalan therapy.
abstract: We have previously demonstrated that depletion of CD8+ T-cells by the use of a monoclonal anti-Lyt-2.2 antibody abolishes the curative effectiveness of low-dose melphalan (L-phenylalanine mustard; L-PAM) therapy for BALB/c mice bearing a large (greater than or equal to 20 mm) s.c. MOPC-315 tumor and extensive metastases (Mokyr et al., Cancer Res., 49: 4597-4606, 1989). Here we show that as a consequence of low-dose L-PAM therapy, CD8+ T-cells accumulate in the s.c. tumor nodules of MOPC-315 tumor bearers. Specifically, an 80-fold increase in the number of CD8+ T-cells was seen within 5 days after the chemotherapy. Treatment of MOPC-315 tumor bearers with low-dose L-PAM in conjunction with monoclonal anti-Thy-1.2 or anti-Lyt-2.2 antibody, in contrast to treatment with monoclonal anti-L3T4 antibody, prevented the appearance of the massive CD8+ T-cell infiltrate in the s.c. tumor nodules. Fresh CD8+ T-cells derived from s.c. MOPC-315 tumor nodules that were regressing as a consequence of low-dose L-PAM therapy exhibited a potent direct lytic activity against the MOPC-315 plasmacytoma in a short-term in vitro assay. The specificity of the lytic activity exhibited by the CD8+ T-cells was illustrated not only by the inability of the CD8+ T-cells to lyse two antigenically unrelated thymomas (the WEHI 22.1 and the EL-4) and a natural killer-sensitive lymphoma (the YAC-1), but also by their relatively weak lytic activity against an antigenically related plasmacytoma (the MOPC-104E). Thus, CD8+ T-cells that infiltrate the s.c. tumor nodules of MOPC-315 tumor bearers following low-dose L-PAM therapy most likely exploit a CTL-type lytic mechanism to eradicate at least part of the large tumor burden not eliminated by the direct antitumor effects of the drug.
authors.affiliation: Department of Microbiology and Immunology, University of Illinois, Chicago 60680.
authors.forename: B Y
authors.initials: BY
authors.lastname: Takesue
authors.forename: J M
authors.initials: JM
authors.lastname: Pyle
authors.forename: M B
authors.initials: MB
authors.lastname: Mokyr
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D016827:CD8 Antigens; D005260:Female; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008223:Lymphoma / Q000188:drug therapy / Q000276:immunology; D008558:Melphalan / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010954:Plasmacytoma / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D013945:Thymoma / Q000188:drug therapy / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D016827:CD8 Antigens; D008558:Melphalan