FINAL EXAM Flashcards
Name the four major components of the cellular barrier and describe the main differences between each of them
Neutrophils, macrophages, dendritic, cells and natural killer cells.
Neutrophils, macrophages, and dendritic cells are phagocytes while natural killer cells are cytotoxic effector cells. Neutrophils conduct the first wave of phagocytosis, but they don’t live long. Macrophages are the big eaters and they can phagocytose a larger quantity of pathogens compared to neutrophils. Dendritic cells usually arrive later and they play a key role in the activation of the adaptive immune system by antigen presentation
Name the two major physical components and explain in a few words why they play an essential role in innate immunity
Skin and mucous membranes. These two structures are our first line of defence. They create, with mucous, cilia, and chemical components, a barrier that is difficult for pathogens to break through.
What is the complement system made of? Name its three main functions in innate immunity.
The complement system is made of over 30 soluble proteins. The main functions of the complement system in innate immunity are:
1. opsonization which induces phagocytosis
2. chemotaxis which induces inflammation
3. lysis through its membrane attack complexes.
Name the major steps of the inflammatory response and briefly describe their role when a pathogen breaks through the physical barrier. +3 purpose of inflammation
- Breach- pathogen/injury breaks physical barrier
- Vasodilation- increase BF, increase immune cells and nutrients to area
- Permeabilization- blood vessels become leaky, allows fluid/proteins into tissues (swelling)
- Chemotaxis- chemical signals attract immune cells to site
- Margination- immune cells stick to endothelial walls of blood vessels
- Extravasation- immune cells move from blood vessels into tissues
- Phagocytosis- pathogens engulfed and destroyed by phagocytes
3 functions:
-localize and contain infection/injury
-eliminate pathogens
-initiate tissue repair
*‘Big Vegans Prefer Crunchy Meatballs Every Plate’
Name and briefly describe each of the five key steps in the process of phagocytosis.
- Attachment- phagocyte recognizes and binds to pathogen
- Ingestion- pathogen ingested and vacuole formed around it called phagosome
- Fusion- phagosome fuses with lysosome and releases lysosomal enzymes
- Digestion- pathogen is destroyed and digested by the lysosomal enzymes
- Release- waste products released from cell via exocytosis
*‘Aliens Inhale Fresh Donuts Rapidly’
*What are TLRs? How do they contribute to the immune response and what branch does it belong to
TLRs (toll like receptors) are a class of PRRs (pattern recognition receptors) which are essential for the innate immune response.
Their two major roles are to recognize PAMPs and DAMPs, and induce signalling to activate T-cells
Process:
-TLRs sense infection through PAMPs and/or DAMPs, bacterium engulfed through phagocytosis
-Antigen presenting cell presents pieces of pathogen on its surface via MHC and increases production of co-stimulatory molecules
-Naive T-cells bind to MHC through T-cell receptor and activates the T-cell to initiate the adaptive response
*Explain antigen presentation via the exogenous pathway
-used when targeting a pathogen in the external environment (bacteria)
- Engulfment- APCs engulf foreign antigen
- Proteolytic processing- foreign antigen in endosome broken down into fragments
- Formation of MHC- antigen complex- vesicle with fragments fuses with vesicles with MHC molecules from ER, forming MHC-antigen complexes
- Cell surface expression- MHC antigen complex transported to plasma membrane to be displayed at the surface
- Recognition by Helper T-cell- TCR on surface of helper t-cell binds to MHC-antigen complex on surface of APC, initiating adaptive response
*exogenous pathway forms peptide:MHC class II complex (organized by CD4+ Helper T-cells)
“Exciting Penguins Form Cool Relationships”
*Explain antigen presentation via the endogenous pathway
Briefly, the endogenous pathway allows the cell to process self or foreign intracellular particles and present them at the cell surface in order to be recognized by T-cell receptors on cytotoxic T-cells.
Forms peptide: MHC class I complex (recognized by CD8+ cytotoxic T-cells)
*exogenous pathway more focused on in the course
What is the importance of T-cell dependent B-cell activation and B-cell binding free antigens to generate an immune response?
Immune system requires assistance of CD4+ helper T-cells to induce humoral immunity and differentiation of B-cells into plasmocytes and memory B-cells.
3 signals of this pathway:
1. TCR-Peptide: MHC complex- B-cells present processed antigen on MHC class II to CD4+ helper T-cells, T-cell receptor binds to peptide MHC complex on B-cell
2. Co-stimulation- CD40:CD40L and B7:CD28 binding (B-cell:T-cell) inducing co-stimulatory signal in both cells
3. Cytokines- activated helper T-cells secrete cytokines
IN OTHER WORDS:
Antigen Presentation: B-cells internalize and process antigens, then display them on MHC class II molecules.
TCR Recognition: A CD4+ helper T-cell recognizes the antigen-MHC complex through its T-cell receptor (TCR).
Co-stimulation: The B-cell provides additional signals (e.g., CD40-CD40L interaction) to fully activate the T-cell.
Cytokine Release:
Activated T-cells release cytokines to amplify immune responses, including activating other immune cells.
*these steps cause proliferation and differentiation of B-cells into plasmocytes (to produce antibodies) and memory B-cells (for long-term immunity)
Immune surveillance and immune editing
Immune surveillance= acts as a detection mechanism, immune system works to monitor for abnormal cells such as tumours and infected cells, and eliminate them to prevent disease.
Immune-editing= 3 phase process that explains tumour adaptation and evasion. Includes steps of:
1) Elimination- When a tumour cell arises in a tissue, the immune system can quickly act to remove it. A variety of immune cells, including NK cells, cytotoxic T-cells, and helper T-cells, can recognize the altered cell and work to eliminate it.
2) Equilibrium- If the tumour cells are not eliminated, they can enter a state of equilibrium where the cell proliferation is matched by cell killing by the immune system. This equilibrium phase can last for a short time or many years.
3) Escape- Finally, in the escape phase, tumour cells are no longer recognized by the immune system and so avoid elimination. These cells are able to grow uncontrolled and eventually proliferate to form a tumour.
4 Advantages of Immunotherapy
One advantage of immunotherapy is that it can be applied to ALL types of cancer, not restricted to specific types like traditional cancer treatments.
Another advantage is that it allows the human immune system to target cancer cells without damaging healthy cells and this provides less side effects than other cancer treatments which also damage healthy cells.
It takes advantage of immunological memory, allowing for the possibility of long term protection.
It is able to attack cancerous cells throughout all organs in the body.
Briefly describe the pathogenesis (what cells are infected and what does the infection lead to), transmission (major ways of transmission) and epidemiology (where it is commonly found) of the HIV?
Pathogenesis: HIV targets and kills immune cells, including CD4+ T cells and others like DCs and macrophages. It does this by attaching to CD4 and multiplying, which lowers the quantity of CD4+ T cells and impairs the immune system.
Transmission: HIV is transmitted by unprotected sexual contact, blood, and mother-to-child contact during childbirth and/or breastfeeding. Different places have different modes of transmission. Ex. It primarily spreads through non-sterile drug injection in Eastern Europe and Central Asia, North America= sexual intercourse, Sub-sarahan Africa= mother to child
Epidemiology: HIV affects millions of people worldwide, certain groups are more vulnerable than others. For instance, people who engage in unprotected intercourse more likely to contract HIV. Current treatments increase life expectancy but do not cure HIV.
*2 ways cancer evades the immune response
- Reduced MHC Expression:
Tumour cells display low levels of MHC I, therefore can’t be recognized by cytotoxic T-cells for elimination - Poor Co-stimulatory Molecules:
required for T-cell activation, therefore without them results in poor immune responses
*Cancer immunity cycle and how cancer surveillance is accomplished. Give an example. (7 steps)
Cancer surveillance= ability of the immune system to identify cancer and monitor it (explained by the initiation of the cancer cycle)
Cancer immunity cycle:
1. Cancer cells release pathogen (cancer cell dies)
2. Pathogen expressed on APC after engulfment and the immune cell carries the epitope to the lymph nodes
3. Priming and activation- naive helper T-cells interact with peptides to initiate response
4. Trafficking of cytotoxic T-cell to tumour
5. Invasion of cytotoxic T-cell into tumour
6. Cytotoxic T-cell recognizes tumour cells from previous exposure to antigens
7. Cancer cells killed
4 types of vaccines
- Live-attenuated vaccine
-modified strain of pathogen, initiates immune response through replication without leading to disease
-prolonged exposure but potential to revert to virulent form and needs specific storage (measles) - Killed-inactivated vaccine
-contains strain of pathogen killed by heat, chemicals or radiation able to generate immune response but not replicate. Safer and easy to store, but need booster shots and injection (rabies, flu) - Toxoid vaccine
-contains inactivated toxin, safe and stable but needs multiple doses (tetanus, Diptheria) - Subunit vaccine
-contains small part of pathogen, safest type but less successful at long lasting immunity (Hepatitis B)
