title: Immunotherapy of a murine tumor with interleukin 2. Increased sensitivity after MHC class I gene transfection.
abstract: We have shown that two weakly immunogenic MCA sarcomas developed in our laboratory that are sensitive to high-dose IL-2 immunotherapy express class I MHC in vivo and in vitro. Two nonimmunogenic MCA sarcomas are relatively insensitive to IL-2 therapy and express minimal or no class I MHC molecules in vivo and in vitro. To study the role of MHC in the therapy of tumors with IL-2, a class I-deficient murine melanoma, B16BL6, was transfected with the Kb class I gene. Expression of class I MHC rendered B16BL6 advanced pulmonary macrometastases sensitive to IL-2 immunotherapy. 3-d micrometastases of CL8-2, a class I transfected clone of B16BL6, were significantly more sensitive to IL-2 therapy than a control nontransfected line. Expression of Iak, a class II MHC molecule, had no effect on IL-2 therapy of transfectant pulmonary micrometastases in F1 mice. By using lymphocyte subset depletion with mAbs directed against Lyt-2, therapy of class I transfectant macrometastases with high-dose IL-2 was shown to involve an Lyt-2 cell. In contrast, regression of micrometastases treated with low-dose IL-2 involved Lyt-2+ cells, but regression mediated by high doses of IL-2 did not. We hypothesize that both LAK and Lyt-2+ T cells effect IL-2-mediated elimination of micrometastases, but only Lyt-2+ T cells are involved in macrometastatic regression. Low doses of IL-2 stimulate Lyt-2+ cells to eliminate class I-expressing micrometastases, but high doses of IL-2 can recruit LAK cells to mediate regression of micrometastases independent of class I expression. Only high-dose IL-2, mediating its effect predominantly via Lyt-2+ cells, is capable of impacting on MHC class I-expressing macrometastases. Macrometastases devoid of class I MHC antigens appear to be resistant to IL-2 therapy.
mesh_terms: D000818:Animals; D000950:Antigens, Ly / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D006183:H-2 Antigens / Q000235:genetics / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology; D007111:Immunity, Cellular; D007167:Immunotherapy; D007376:Interleukin-2 / Q000627:therapeutic use*; D007694:Killer Cells, Natural / Q000276:immunology; D008285:Major Histocompatibility Complex; D008546:Melanoma, Experimental / Q000276:immunology / Q000628:therapy*; D051379:Mice; D009362:Neoplasm Metastasis; D012333:RNA, Messenger / Q000235:genetics; D012513:Sarcoma, Experimental / Q000276:immunology / Q000628:therapy; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection
chemical_list: D000950:Antigens, Ly; D006183:H-2 Antigens; D000949:Histocompatibility Antigens Class II; D007376:Interleukin-2; D012333:RNA, Messenger