Active Immunoprophylaxis and Immunotherapy in Two Mouse Lymphoma Models2

Abstract

Injections of appropriate numbers of irradiated tumor cells produced antibodies against tumor cell-surface antigen(s) in both syngeneic tumor models studied: the early transplant generations of the spontaneous L2 lymphoma in AKR/J mice and the chemically induced EL 4 lymphoma in C57BL/6J mice. No antibody was detected in normal or nonimmunized tumor-bearing mice. Tumor inhibitory or enhancing activity was not demonstrated by these antibodies. Immunoprophylaxis or cell-mediated immunity against the L2 lymphoma was not observed after injections of irradiated L2 cells and/or BCG into AKR mice. However, injections of irradiated EL 4 cells alone were effective in immunoprophylaxis against as many as 10(6) EL 4 cells and in immunotherapy against 10(2) EL 4 cells per mouse. The addition of BCG injections made immunotherapy with irradiated EL 4 cells effective against a load of 10(4) EL 4 cells/mouse, though BCG alone was not effective for immunoprophylaxis against EL 4 cells. Resistance to EL 4 could be transferred with viable syngeneic peritoneal or nucleated spleen cells. In both tumor models, an ongoing delayed hypersensitivity reaction to BCG alone apparently did not inhibit bystander tumor cells even when tumor cells were mixed before inoculation with viable BCG. In neither tumor model were concanavalin A-coated tumor cells more potent for immunoprophylaxis than were irradiated tumor cells alone.

Inhibition of pulmonary metastases of B16 melanoma with irradiated tumor cells and BCG

“…Delayed hypersensitivity to BCG and tumor cells was assayed as described before [9,10]. In brief, 0.03 ml HBSS containing either irradiated tumor cells (108 cells/ml suspension) or 1.5 mg BCG (heat-inactivated at 56 ° C for 30 min) was injected ID into the left footpad of immune or previously untreated control mice.…”

“…Footpads excised from normal and immunized mice at 24, 48, and 72 h after challenge were fixed in 10% formalin. Sections from paraffin blocks were stained with hematoxylin and eosin or carbol fuchsin to detect acid-fast bacilli [9].…”

“…Cell-mediated tumor immunity was also evaluated by a Winn-type assay [9,10]. Tumor cells were mixed with nucleated spleen cells from the immunized mice at specified ratios.…”

“…Cytoplasmic and membrane immunofluorescence assays of mouse tumor cells and other control preparations were performed using fluoresceinated goat antiserum against mouse globulin (Hyland Laboratories, Los Angeles, CA, USA) [9,10]. Complement-dependent cytotoxicity was assayed by trypan blue permeability of tumor cells incubated with test sera and rabbit complement [9,10].…”

“…Immunotherapy, at best, can eradicate only a small number of tumor cells [9,10,18] and is therefore more suited to the eradication of micrometastases than to the treatment of lesions with large tumor loads. We report here the inhibition of pulmonary micrometastases of B16 melanoma in BCG-sensitized syngeneic C57BL/6J mice after immunotherapy with SC injections of irradiated tumor cells and BCG.…”