Avoiding immune destruction Flashcards
what mouse model was evidence that tumours can be repressed by the immune system?
tumour transplantation models.
immunity was only seen in prophylactic immunization and not therapeutic
once a mouse had been implanted with the tumour, immunization with irradiated cancer cells did nothing to stop tumour growth
what does this mouse model support the existence of?
tumour associated antigens
immunosurveillance theory where carcinomas are constantly eradicated from the immune system
TF: macrophages are only anti tumour
false can be either depending on signals
how can macrophages be anti-tumour?
present the antigen to the T helper cell and trigger tumour cell killing by antibodies
which 2 signals can activate macrophages in a anti tumour way?
bacteria lipopolysaccharide
interferon gamma
what can trigger macrophages in a pro tumour way?
hypoxia and other physiological signals released by tumours.
macrophage subtype M__ promotes immune attack on tumours and the subtype M__ promotes tumour progression
M1
M2
what initiates the process of phagocytosis and destruction of infected cells by the immune system?
coating of mammalian cells by antibody molecules due to the cell presenting target antigens
what do natural killer cells do once the mammalian cell is covered by antibodies. what does this activate?
natural killer cells uses its Fc cell surface receptor to bind to the constant regions of the antibody molecules
this activates the NK cell which then destroys the target cell by releasing cytotoxic granules
what is antibody dependent cell mediated cytotoxicity
the way NK cells kill cells using cytotoxic granules, Due to antibodies being present on the surface of cells presenting antigens
which cells tend to notably present antigens?
dendritic cells
where do langerhans reside?
in the skin
what do langerhans do?
take up antigens by phagocytosis and takes them to the lymph nodes
here they mature to dendritic cells and present the antigen to T cells triggering an immune response against this antigen.
dendritic cells activate which cells?
Th and Tc
what happens when a dendritic cell finds a T helper cell which recognises the antigens it (the dendrite) is presenting
the T helper cell becomes activated which leaves to find B-cells also displaying this surface antigen
once the T helper cell finds a B cell presenting the antigen which the dentrite has presented to the T cell, what happens?
the B cell proliferates and differentiates into plasma cells which release antibody molecules
what is the interaction between dendritic cells and cytotoxic T cell precursors called? what effect does this have on the cytotoxic T cell precursors?
cross presentation
helps the precursors mature into active cytotoxic T cells
what do cytotoxic granules from Tc contain?
perforin and granzyme B
5 Mechanisms by which tumours escape immune recognition?
- low immunogenicity
- tumour treated as self antigen
- antigenic modulation
- tumour induced immune suppression
- tumour induced privileged site
explain how low immunogenicity can help the tumour
low expression of adhesion molecules or MHC’s so appear normal to the immune system
explain how the tumour is treated as a self antigen to evade immune response
APCs present the tumour antigens in the absence of co-stimulatory signals- this makes the T cells tolerative of them so they dont attack
explain how antigenic modulation helps a tumour evade the immune response
tumour initially express antigens which the immune system response to but can lose them by: ‘antibody induced internalisation’ or ‘antigenic variation’
2 ways tumours can lose their antigens to evade the immune system?
antibody induced internalisation
antigenic variation
what products can tumour cells make to suppress the immune system?
TGF-b
