Characterization of variant and parental-cross-protective immunity to immunogenic variants of a murine fibrosarcoma using the local adoptive transfer assay

Abstract

The purpose of this study was to characterize the lymphocyte populations responsible for rejection of immunogenic (Imm+) tumor variants, and the cross-protective immunity engendered by Imm+ variants against the weakly immunogenic parental tumor. Immunogenic clones of the weakly immunogenic methylcholanthrene-induced fibrosarcoma MCA-F have been generated using 1-methyl-3-nitro-1-nitrosoguanidine, 5-aza-2'-deoxycytidine, or ultraviolet radiation (UV-B; 280-320 nm). These clones grow progressively in immunosuppressed adult-thymectomized irradiated mice, but are rejected by immunocompetent syngeneic hosts. The parental MCA-F tumor grows progressively in both groups. Mice that have rejected a challenge of 1 x 10(5) Imm+ cells show an anamnestic immune response against both the Imm+ clone and the parental MCA-F tumor. Using the local adoptive transfer assay and depletion of T-cell subsets with antibody plus complement, we show that immunity induced by the Imm+ variants against the parent MCA-F was mediated by the Thy1.2+, L3T4a+ population without an apparent contribution by Lyt2.1+ cells. Although antivariant immunity was also dependent upon Thy1.2+ cells, depletion of either the L3T4a+ or the Lyt2.1+ cells failed to abolish immunity against the variant. A role for Lyt2.1+ T lymphocytes in antivariant immunity, but not antiparent immunity, was supported by the results of cytotoxic T lymphocyte (CTL) assays. Following immunization with high numbers (1 x 10(5) to 5 x 10(5) of viable Imm+ cells, antivariant, but not antiparent CTL activity was detected in mixed lymphocyte tumor cell cultures. Immunization with lower numbers (3 x 10(4] of viable Imm+ or with high numbers of mitomycin-C-treated Imm+ engenders only antivariant immunity without parental cross-protection. Under these conditions lymphocytes mediating immunity against the variant in the local adoptive transfer assay were exclusively of the Thy1.2+, L3T4a+ phenotype, with no contribution from the Lyt2.1+ cells. Identical results were obtained for Imm+ clones of MCA-F induced by methylnitronitrosoguanidine, 5-azadeoxycytidine, and UV-B, suggesting that the nature of the antitumor immunity engendered by Imm+ is not significantly affected by the agent used. Furthermore, these results demonstrate that the cross-reactivity and cellular effectors of antitumor immunity in this system are influenced by the immunizing dose of Imm+ cells: the predominant effectors of both antivariant and parental-cross-reactive immunity were of the CD4+ T cell subclass, with a CD8+ cytotoxic population contributing to antivariant immunity only after high-dose immunization.

Murine epidermal Langerhans cells and splenic dendritic cells present tumor‐associated antigens to primed T cells

“…In several tumor models, anti-tumor CD4+ T cells have proven capable of mediating tumor rejection or conferring protective immunity, even in the absence of CD8+ Tcells [12,[22][23][24]. Although CD4+ Tcells are non-cytolytic to most tumors, it has been demonstrated that direct cytolytic effects are not essential for the anti-tumor activity of CD4+ [22] or even CD8+ T cells [31].…”

“…There is evidence that dendritic APC themselves may play a greater role in the processing and presentation of at least certain Ag in vivo than monocytes/macrophages [16]. In particular, LC are critical for both the afferent and efferent limbs of contact hypersensitivity and transplantation rejection [9,17,181 and may play an essential role in anti-tumor immunosurveillance [19-211. That MHC class-I1 bearing APC primarily stimulate CD4+ Tcells is of particular interest, since in several tumor models anti-tumor CD4+ T cells or non-CD8+ T cells have proven capable of mediating tumor rejection or conferring protective immunity [12,[22][23][24]. In these models, the successful culture of anti-tumor CD4+ T cells has relied on immunization of animals against a tumor or purified tumor protein and subsequent in v i m restimulation of sensitized Tcells with macrophages or spleen cells pulsed with a purified tumor protein [22,251.…”