Chapter 12 and 13: Immunology, immunotherapy and inflammation (Lecture 2/2, main) Flashcards
Tumor vaccination can be ex vivo/conventional vaccination or in vivo/in situ vaccination. Explain the process of conventional vaccination.
In ex vivo/conventional vaccination an identified tumor antigen is used together with an adjuvant. It is then systemically injected into the body where it will be taken up by APCs which causes activation and expansion of effector T cells that recognize the specfic vaccine antigens and can fight the tumor.
Tumor vaccination can be ex vivo/conventional vaccination or in vivo/in situ vaccination. Explain the process of in vivo/in situ vaccination.
Here, the vaccine only consists of an adjuvant. The vaccine is injected into the tumor (intratumoral injection). The adjuvants boosts the immune system and exploits all relevant tumor antigens avaible in the tumor. This causes activation and expansion of effector T cells that can recognize all relevant tumor antigens.
Oncolytic viruses (like the adenovirus) can be used in treatment of cancer. Explain how an oncolytic virus can kill cancer cells but keep normal cells intact.
Oncolytic viruses are molecularly changed so that they cannot divide in normal cells, but can in cancer cells. This is because cancer cells have activated pathways that protects them against apoptosis. Oncolytic viruses can replicate in cancer cell and upon virus release the cancer cells gets destroyed (lysis). The new virus particles can infiltrate new cancer cells and kill these as well.
How are oncolytic virusses also able to activate an anti-tumor immune response?
With the lysis of cancer cells and the release of virus particles, cancer antigens will be released that activate the immune system. They also carry TLR ligands that can help in activation of dendritic cells.
What’s the difference between active and passive immunotherapy?
The aim of active immunotherapy is to stimulate the host’s immune system or a specific immune response to a disease/pathogen (most used in cancer treatment). The aim of passive immunotherapy is to boost and help the immune system in fighting off an infection or disease, this is usually done with the help of antibodies.
Steve Rosenberg became known for his treatment against melanomas. What kind of immunotherapy did he came up with (active/passive) and how did he came up with this treatment?
He came up with passive immunotherapy –> vaccination with in vitro primed/expanded T cells. He excised tumors from a patient which he fragmented. The fragments of these tumor were then cultured in the lab with IL-2 (growth factor for T cells) which caused T cells to activate and proliferate. The T cells were then examined whether they could recognize the specific tumor antigens and where then put back into the body.
What was the thing that at last made the immunotherapy of Steve Rosenberg work?
Before injections of the tumor antigen specific T cells, the patients get treated with standard chemotherapy or radiation (lymphodepleting chemotherapy). This causes complete destruction of (among others) T cells. When the tumor antigen specific T cells are injected, they don’t need to compete with other ‘normal’ T cells and thus make them more effective.
What treatment is there if you have a tumor that’s not operable (so it’s not possible to isolate tumors, like in the therapy of Steve Rosenberg)?
CAR T cell therapy
CAR T cells stand for Chimaeric Antigen Receptor T cells. They are used in CAR T cell therapy. How are CAR T cells generated?
In this treatment antibody fragments that bind to specific antigens are fused to the end of a T cell receptor (TCR). The antibody is transduced into the T cell with the help of a retrovirus.
How does CAR T cell immunotherapy work?
Blood is extracted and leukopheresis is performed. You grow out the T cells with the help of IL-2. Through retroviral transduction anti-CD19 CAR (antibody) is transduced into the T cells. Lymphodepleting chemotherapy is performed on the patients and the anti-CD19 CAR T cells are injected into the body. And when this complex recognizes the specific tumor antigens that anti-CD19 CAR can bind, the T cells become active.
How can inflammation indirectly cause DNA damage?
Injury/irritation/infection will result in an inflammatory reaction (recruitment of mast cells, neutrophils and monocytes). These immune cells respond with a respiratory burst (essential for e.g. degradation of pathogens) and release of free radicals. These can cause protein damage, lipid peroxidation and DNA damage and mutation.
Immune cells interact with the tumor with the help of cytokines. Cytokines can have pro- and anti-tumor effects. Name cytokines that suppress tumor growth (functions will be discussed in detail later).
IL-12 (and IL-23)
Immune cells interact with the tumor with the help of cytokines. Cytokines can have pro- and anti-tumor effects. Name groups of cytokines that progress tumor growth (functions will be discussed in detail later).
- TNF-a, IL-6 and IL-10
- TGF-b
- TNF-a, IL-6 and TGF-b
- TNF-a, IL-17 and TGF-b
- TNF-a and TGF-b
(TNF-a, IL-6, IL-10, TFG-b and IL-17)
The cytokine IL-12 suppresses tumor growth. How?
IL-12 activates NK cells and cytotoxic T cells.
What is the function of TNF-a, IL-6 and IL-10?
They enhance tumor cell growth.
The cytokine TGF-b enhance tumor growth. How?
It enhances tumor cell tissue invasion.
The cytokines TNF-a, IL-6 and TGF-b enhance tumor growth. How?
They affect stromal cells and enhance metastasis.
What is elimination in immuno-editing?
Tumor cells don’t spontaneously arise and grow. Elimination is the response of the immune system to the arising tumor cells by activation of all kinds of immune cells (NK, CD8+, CD4+, macrophages etc.) which results in the elimination of these tumor cells.
What is equilibrium in immuno-editing?
Some tumor cells have gained mutations and have the ability to escape the immune response. So in equilibrium some cells can start to grow (the ones that can evade the immune system) and some get destroyed by the immune system.
What is escape in immuno-editing?
Accumulation of mutations occur over time in the surviving cancer cells. This will in the end cause complete immune evasion of cancer cells (e.g. by antigen or MHC loss). Cancer cells can then invade and metastasize.
The last flashcard mentioned 10 ways tumors evade the immune system. The last two (immunosuppression by tumor-derived factors and DC suppression/depletion + MDSC accumulation) are major problems and need new vaccination strategies to circumvent these problems. Why are they such a big problem?
A tumor suppresses the immune system by releasing tumor-derived factors that can suppress the immune system (like IL-10 and IL-6). When a tumor metastasizes these tumor-derived factors can become systemic and can (for example) widely suppress dendritic cells to become mature. This causes accumulation of myeloid dendritic suppressor cells (MDSC) that suppress T cell proliferation.
Do you expect T cell tolerance and immune suppression in melanomas? Why?
Melanomas have a high somatic mutation rate and thus try the hardest to escape the immune system. In these tumors you can find loads of immune cells that all have a hand in suppressing the immune system (Treg, Th2, suppressive cytokines, mono- and granulocytic MDSC). Note that this phenomenon can also be found in draining lymph nodes.
Tumors can suppress the immune system by downregulating MHC class I molecules. But cells that have downregulation of MHC class I can react to this to prevent immune suppression. What reaction is this?
NK cells become active (NK cells are important in killing of virusses who also have gotten better in downregulating MHC molecules).
How can a heterogeneous tumor with a HLA-negative tumor nest (due to β2m (constituent of MHC complex) mutation) result in a homogeneous HLA-negative metastasis?
The primary tumor consists of a few cells that are HLA-negative and thus have a β2m mutation and consists of cells that still express the HLA molecules (and thus no mutation). The primary tumor is therefore called heterogeneous. These cells can escape the immune system, have more ability to divide and thus can metastasize. The metastasis then consists of homogeneous HLA- negative cancer cells that all have escaped the immune system.
There are different phenotypes for HLA class I loss in cancers. Describe the following phenotypes and keep in mind that an HLA molecule contains two different haplotypes of different subunits (Cw2 and Cw7 for example):
- HLA total loss
- HLA haplotype loss
- HLA locus loss
- HLA allelic loss
- Compound phenotype
- Unresponsiveness to IFNs
- HLA class Ia +/- HLA class Ib +
- HLA total loss: there’s total HLA loss if all subunits of a HLA molecule have been lost
- HLA haplotype loss: if there’s haplotype loss this means that there’s loss of alleles that are inherited together from a single parent. So this means that if you get Cw7, A2 and B7 from your mother and Cw2, A24 and B44 from your father, that there can be haplotype loss if Cw7, A2 and B7 are not present anymore.
- HLA locus loss: this means that the genes located on the loci on both chromosomes are lost, for example loss of A2 and A24.
- HLA allelic loss: HLA allelic loss is loss of one specific gene of one chromosome (for example only loss of B44).
- Compund phenotype: a combination of HLA allelic/locus/haplotype loss.
- Unresponsiveness to IFNs: tumor cells carry mutations in the IFN pathway that blocks upregulation of MHC molecules.
- HLA class Ia +/- HLA class Ib +: a certain phenotype that can bind to c-myc on T cells and suppresses them.
T cells become active when an antigen is presented to them through an APC. But they can also be suppressed through interaction and binding of PD-1 on the T cell to its’ ligand PDL-1 on the APC. What happens when PD-1 binds with its ligand PDL-1?
Intracellular cascade that will lead to the blockade of activation of the TCR and costimulatory molecules. This causes reduced TCR signaling, cytokine production and target cell lysis.
How is CTLA4 on T cells able to block an immune response?
By competing for the binding to B7-1 (CD80) on the APC with CD28. CTLA4 has a higher affinity and outcompetes CD28 and thus blocks activation.
PD-1 and CTLA4 drugs seem to work best in different stages of tumor progression.
Why is CTLA-4 a target in draining lymph nodes and why is PD-1 (and PD-L1) a target in the tumor environment?
- Because CTLA-4 outcompetes CD28, CD28 is the first co-stimulatory molecule to be blocked. When this signal isn’t blocked, it is important in initiating T cell response in the lymph node. Thus binding of CTLA-4 to B7, is the first to aid cancer in carcinogenesis. Therefore, targeting CTLA-4 in draining lymph nodes is most effective.
- Binding of the ligands of PD-1 (and PD-L1) are responsible for inactivating effector T cells (T cells have already been primed and activated in lymph nodes). Therefore, targeting PD-1 and PD-L1 in the tumor environment, where T cell functions have been inactivated due to ligand and PD-1 interaction, is most effective.
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