Open Access Te Herenga Waka-Victoria University of Wellington
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Immune Responses in Perforin Deficient Mice

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posted on 2021-11-10, 02:29 authored by Simkins, Helen Mary Alys

Dendritic cells (DC) play a pivotal role in the initiation of T cell responses and earlier studies have shown that their survival is important for the generation of effective immune responses. Cytotoxic T lymphocytes (CTL) and natural killer T (NKT) cells have been proposed to regulate the survival of antigen presenting DC through their ability to kill cells expressing specific antigen via secretion of perforin, a protein contained in cytotoxic granules. Perforin knockout (PKO) mice generate amplified immune responses to DC immunization, suggesting a link between defective cytotoxicity and increased T cell responses. The studies in this thesis used PKO mice and in vivo models of CD8+T cells and NKT cell immune responses to determine whether CTL and NKT cells eliminate DC in a perforin-dependent manner, and whether DC elimination is a mechanism to regulate T cell responses. During a primary influenza infection C57BL/6 and PKO mice generated a similar influenza specific CD8+ immune response. No significant difference in the percentage of influenza epitope PA224-233 specific T cells was observed between C57BL/6 and PKO mice during a secondary influenza infection, but PKO mice had a significantly reduced T cell response directed towards the dominant influenza epitope, NP366-374. The reduced T cell response in PKO mice was not due to differences in activation or differentiation status of specific T cells compared to C57BL/6 mice. Therefore, the extended DC survival in PKO after secondary influenza viral infection, recently reported by other authors, does not appear to correlate with increased expansion of virus specific CD8+T cells in infected mice. The role of NKT cells in DC elimination was assessed in vivo using the NKT cell ligand a-Galactosylceramide (a-GalCer). Injection of a-GalCer in C57BL/6 mice induced a dramatic decline in the number of splenic CD8+DC. A similar decrease in CD8+DC numbers was observed in PKO mice, suggesting that the mechanism of DC loss did not involve perforinmediated killing. In contrast, treatment with a TNF-a neutralizing antibody substantially reduced the decline in CD8+DC numbers. This reduction in splenic CD8+DC occurred as early as 15 hr after a-GalCer treatment, and did not affect generation of CD8+T cell responses or the ability of a-GalCer treatment to provide tumour protection. Taken together, these results suggest that multiple cells and mechanisms can regulate DC survival in vivo. CTL regulate DC survival in vivo in a perforin-dependent manner, but this does not necessarily affect the magnitude of the resulting immune responses. NKT cells also affect the survival of DC in vivo, but in a perforin-independent, cytokine-dependent manner. These findings provide additional knowledge about the in vivo involvement of perforin in regulating DC survival by CTL and NKT cells and the effects this has on T cell responses.


Copyright Date


Date of Award



Te Herenga Waka—Victoria University of Wellington

Rights License

Author Retains Copyright

Degree Discipline

Cell and Molecular Bioscience

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level


Degree Name

Doctor of Philosophy

Victoria University of Wellington Item Type

Awarded Doctoral Thesis



Victoria University of Wellington School

School of Biological Sciences


Ronchese, Franca; Kirman, Joanna