In vitro and in vivo correlates of hybrid tumor resistance
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Abstract:
Tumorigenicity of 2 sublines, TU1 and TM5, of the C.B6-H-2dm4 (dm4) mouse tumor, TDM4, was tested in dm4 and F1 hybrid mice (from crosses of dm4 with a variety of other strains) to determine the genetics of hybrid resistance to these 2 tumor sublines. Resistance to TU1 was associated with at least 3 genes and required heterozygosity in the H-2D region, with secondary effects attributable to H-2K genes and non-H-2 genes. Resistance to TM5, however, did not require H-2D region heterozygosity, whereas H-2K and non-H-2 genes appeared to have significant effects. For evaluation of possible mechanisms for hybrid resistance, 4 assay systems were used. Comparison of natural killer cell activity in dm4 and various hybrid mice revealed no consistent activity against either TU1 or TM5. Little correlation was seen between resistance and generation of strong T-lymphocyte proliferative responses to the sublines. Likewise, cytotoxic T-lymphocyte (CTL) activity, particularly against TU1, was not associated with increased resistance. In contrast, delayed-type hypersensitivity (DTH) was consistently greater in hybrids with increased resistance to either subline. These results suggest a strong association between DTH responsiveness and hybrid resistance. Furthermore, the association, in some hybrids, of CTL activity with resistance to the TM5 subline, but not to TU1, may mean that different sublines of the same tumor can induce different sets of immune responses.
Insights
Hybrid resistance to mouse tumors involves complex genetics, with different tumor sublines triggering distinct immune responses. Delayed-type hypersensitivity (DTH) strongly correlates with hybrid resistance, unlike natural killer cell or T-lymphocyte activity.
Area of Science:
- Immunology
- Genetics
- Cancer Research
Background:
- Hybrid resistance is a phenomenon where F1 hybrid mice exhibit enhanced immunity against certain tumors compared to parental strains.
- Understanding the genetic basis of hybrid resistance is crucial for developing novel cancer immunotherapies.
Purpose of the Study:
- To investigate the genetic control of hybrid resistance to two sublines (TU1 and TM5) of the C.B6-H-2dm4 (dm4) mouse tumor.
- To elucidate the immunological mechanisms underlying hybrid resistance, focusing on natural killer cell activity, T-lymphocyte proliferation, cytotoxic T-lymphocyte (CTL) activity, and delayed-type hypersensitivity (DTH).
Main Methods:
- Tumorigenicity assays were performed in dm4 and F1 hybrid mice.
- Four immunological assay systems were employed: natural killer cell activity, T-lymphocyte proliferation, CTL activity, and DTH.
- Genetic analysis focused on the H-2D, H-2K, and non-H-2 regions.
Main Results:
- Resistance to TU1 required H-2D heterozygosity, with secondary effects from H-2K and non-H-2 genes.
- Resistance to TM5 was independent of H-2D heterozygosity but influenced by H-2K and non-H-2 genes.
- DTH responses were consistently higher in resistant hybrid mice, suggesting a strong association with hybrid resistance.
- CTL activity showed a correlation with resistance to TM5 in some hybrids, but not TU1, indicating subline-specific immune responses.
Conclusions:
- Hybrid resistance to mouse tumors is genetically complex and can be mediated by different genetic factors depending on the tumor subline.
- Delayed-type hypersensitivity (DTH) is a key immune mechanism associated with hybrid resistance.
- Different tumor sublines can elicit distinct immune responses, highlighting the heterogeneity of cancer immunity.