Immunology
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Questions and Answers

What is the primary function of C5a in the complement system?

  • Forms pores in pathogen membranes
  • Increases vascular permeability and recruits immune cells (correct)
  • Activates T cells
  • Cleaves C3 to form C3b

Which components come together to form the membrane attack complex (MAC)?

  • C5a, C3, and C9
  • C3a, C5, and C6
  • C3b, C4, and C5
  • C5b, C6, C7, C8, and multiple C9 molecules (correct)

What is the potential outcome when the membrane attack complex (MAC) binds to microbial membranes?

  • Increase in bacterial replication
  • Direct cell death of the pathogen (correct)
  • Prevention of antigen presentation
  • Inhibition of the complement pathway

C3 convertase is formed from the cleavage of which complement component?

<p>C3 (C)</p> Signup and view all the answers

What role do anaphylatoxins play in the immune system?

<p>Increase inflammation and recruit immune cells (A)</p> Signup and view all the answers

What is the primary function of chemokines in the immune response?

<p>To direct the migration of immune cells (C)</p> Signup and view all the answers

Which of the following are recognized functions of acute phase proteins?

<p>Opsonisation of pathogens (A), Binding to and killing pathogens (B)</p> Signup and view all the answers

Which complement protein is known for its role in opsonization and as a blood marker for infection?

<p>C-reactive protein (A)</p> Signup and view all the answers

What is the result of C3 convertase formation in the complement pathway?

<p>Activation of the membrane attack complex (D)</p> Signup and view all the answers

What is the main role of anaphylatoxins in the immune response?

<p>Attract immune cells to the site of infection (D)</p> Signup and view all the answers

Which of the following factors is NOT involved in the coagulation process of the immune response?

<p>C3 convertase (D)</p> Signup and view all the answers

Which of these is a key function of the complement proteins?

<p>Detection and destruction of pathogens (B)</p> Signup and view all the answers

The migration of immune cells in response to chemokines is known as what process?

<p>Chemotaxis (B)</p> Signup and view all the answers

Which statement accurately describes the role of C5a in the immune response?

<p>C5a promotes chemotaxis of immune cells to the site of infection. (C)</p> Signup and view all the answers

What is the primary function of natural killer (NK) cells in innate immunity?

<p>Directly attacking and destroying virus-infected or tumor cells. (B)</p> Signup and view all the answers

During which pathway is the C3 convertase formed?

<p>All of the above pathways can form C3 convertase. (D)</p> Signup and view all the answers

Which of the following functions is associated with anaphylatoxins?

<p>Induction of systemic inflammatory responses. (A)</p> Signup and view all the answers

Which cell type is primarily responsible for the opsonization process in innate immunity?

<p>All of the above. (D)</p> Signup and view all the answers

The complement system activates which critical immune response mechanism?

<p>Cell lysis through the Membrane Attack Complex. (B)</p> Signup and view all the answers

What distinguishes opsonins from other immune proteins?

<p>They enhance the uptake of pathogens by phagocytes. (D)</p> Signup and view all the answers

What is the role of acute phase proteins in the immune system?

<p>Inflammatory response enhancement and pathogen marking. (B)</p> Signup and view all the answers

Which immune cells primarily recognize Class I MHC molecules?

<p>CD8+ cytotoxic T cells (B)</p> Signup and view all the answers

What is the primary role of Major Histocompatibility Complex (MHC) molecules?

<p>To present antigens to T cells (A)</p> Signup and view all the answers

What is required for T cell activation besides antigen recognition?

<p>Costimulatory signals (C)</p> Signup and view all the answers

Which statement best describes the role of dendritic cells in the immune response?

<p>They process and present antigens to T cells in lymph nodes. (D)</p> Signup and view all the answers

How does the Human MHC relate to its polymorphism?

<p>It allows for the recognition of diverse pathogens. (D)</p> Signup and view all the answers

What type of T cell is primarily involved in helping B cells to produce antibodies?

<p>CD4+ helper T cells (A)</p> Signup and view all the answers

Which co-stimulatory molecules are primarily involved in enhancing T cell activation?

<p>CD80 and CD86 (A)</p> Signup and view all the answers

What characteristic of antigen-specific T and B cells is noted in immunology?

<p>They are rare in the overall lymphocyte population. (C)</p> Signup and view all the answers

What is the primary function of Major Histocompatibility Complex (MHC) molecules in the immune response?

<p>To present antigens to T cells for activation (D)</p> Signup and view all the answers

What must occur for B cells to be fully activated?

<p>B cells require antigen binding and T cell help (C)</p> Signup and view all the answers

Which of the following describes a key function of T cell differentiation?

<p>T cell differentiation prepares them to perform specific immune functions (B)</p> Signup and view all the answers

What is the function of Fc receptors on immune cells?

<p>To recognize and bind the Fc region of antibodies (C)</p> Signup and view all the answers

Which of the following is necessary for T cell activation, in addition to antigen recognition?

<p>Co-stimulatory signals from antigen presenting cells (B)</p> Signup and view all the answers

What is the main role of Th1 cells in the adaptive immune response?

<p>To enhance phagocytosis by macrophages (B)</p> Signup and view all the answers

Which mechanism allows T cells to distinguish between self and non-self antigens?

<p>Recognition of MHC-peptide complexes (D)</p> Signup and view all the answers

How does the structure of antibodies contribute to their function in the immune system?

<p>Their structure allows for high specificity to antigens (B)</p> Signup and view all the answers

What is the role of Major Histocompatibility Complex (MHC) in T cell recognition?

<p>It presents processed antigens to T cells. (D)</p> Signup and view all the answers

How do B cells primarily recognize antigens?

<p>By binding to antigens circulating freely or on microbes. (D)</p> Signup and view all the answers

What occurs during T cell differentiation after antigen recognition?

<p>T cells proliferate and differentiate into various effector cells. (A)</p> Signup and view all the answers

What is the function of the Fc region of antibodies?

<p>It interacts with Fc receptors on immune cells to trigger immune responses. (D)</p> Signup and view all the answers

Which statement describes a necessary aspect of T cell activation beyond antigen recognition?

<p>T cells need co-stimulatory signals to be fully activated. (C)</p> Signup and view all the answers

Which effector T cell type is primarily responsible for killing virus-infected cells?

<p>Cytotoxic T cells (CD8+) (B)</p> Signup and view all the answers

What distinguishes regulatory T cells from other T cell types?

<p>They suppress the activity of T cells and B cells. (D)</p> Signup and view all the answers

What type of cells present antigens to T cells as professional antigen presenting cells?

<p>Dendritic cells (A)</p> Signup and view all the answers

What is the primary role of PD-L1/PD-1 inhibitors in cancer therapy?

<p>To enhance T cell activity against tumors (A)</p> Signup and view all the answers

What is the main function of the chimeric antigen receptor (CAR) in CAR T cell therapy?

<p>To recognize and bind to specific proteins on leukemia cells (B)</p> Signup and view all the answers

What is a potential downside of using monoclonal antibodies like Adalimumab in treatment?

<p>They can lead to an increased risk of infections and tumors (A)</p> Signup and view all the answers

How are T cells genetically modified to express CAR in CAR T cell therapy?

<p>Through the introduction of new DNA using a virus (C)</p> Signup and view all the answers

In which conditions is monoclonal antibody therapy, such as Adalimumab, typically used?

<p>For various autoimmune and inflammatory conditions (C)</p> Signup and view all the answers

What does the concept of immunological tolerance primarily refer to?

<p>The immune system's unresponsiveness to self-antigens. (C)</p> Signup and view all the answers

Where does the removal of cells bearing self-antigen receptors occur in the immune system?

<p>In the bone marrow for B cells and in the thymus for T cells. (D)</p> Signup and view all the answers

Which mechanism ensures that the immune system does not attack self-antigens?

<p>Anergy of self-reactive lymphocytes. (A)</p> Signup and view all the answers

How is the diversity of antigen receptors generated in lymphocytes?

<p>By randomly recombining segments of receptor encoding genes. (B)</p> Signup and view all the answers

What happens to lymphocytes that bind their specific antigen during an immune response?

<p>They proliferate and differentiate into effector cells. (C)</p> Signup and view all the answers

Which approach is an example of immunotherapy used to treat diseases?

<p>Vaccination to enhance immune recognition of antigens. (D)</p> Signup and view all the answers

What is the primary role of antigen presenting cells (APCs) in the immune system?

<p>To present antigens to T cells and activate them. (C)</p> Signup and view all the answers

What is a potential consequence of a loss of immunological tolerance?

<p>Autoimmune diseases resulting from attacks on self-tissues. (A)</p> Signup and view all the answers

What is the main consequence of failing to delete self-reactive T cells in the thymus?

<p>Development of autoimmune diseases (B)</p> Signup and view all the answers

How do tumor cells evade the immune response?

<p>By expressing inhibitory ligands (C)</p> Signup and view all the answers

What is the role of checkpoint inhibitors in immunotherapy?

<p>To block negative signals to T cells (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of regulatory T cells?

<p>They can differentiate into effector T cells (D)</p> Signup and view all the answers

What is the primary purpose of using recombinant cytokines in immunotherapy?

<p>To enhance immune cell production (B)</p> Signup and view all the answers

Which of the following conditions is associated with the failure to eliminate self-reactive T cells?

<p>Rheumatoid Arthritis (A)</p> Signup and view all the answers

What impact does PD-L1 have on T cells?

<p>It inhibits T cell activity (A)</p> Signup and view all the answers

What is a key feature of oncolytic virus therapy in cancer treatment?

<p>It induces tumor cell apoptosis directly (B)</p> Signup and view all the answers

Flashcards

Cytokine producing cell

A cell that releases cytokines, signaling proteins that regulate immune response.

Chemokines

A type of cytokine that attracts immune cells to a specific location.

Chemotaxis

The movement of cells along a chemical concentration gradient.

Acute Phase Proteins

Proteins produced in the liver in response to inflammation.

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Complement System

A group of serum proteins that help to detect and destroy pathogens.

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Opsonization

The process of coating pathogens to enhance their uptake by phagocytic cells.

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C-reactive protein

An acute phase protein that acts as an opsonin and activates the complement system.

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Pattern Recognition

The ability of the immune system to recognize specific molecular patterns present on pathogens.

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C3b (complement)

An opsonin that enhances phagocytosis of pathogens by binding to them.

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C3a (complement)

An anaphylatoxin that increases inflammation and vascular permeability.

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Membrane Attack Complex (MAC)

A complex of complement proteins that creates pores in microbial membranes, causing cell lysis.

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C5a (complement)

A chemoattractant and anaphylatoxin that recruits immune cells and increases inflammation.

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Type 1 Interferons

Early antiviral proteins produced by infected cells, making neighbouring cells resistant to viral infection.

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Complement System Activation

The process by which the complement system, a group of proteins in the blood, is triggered to fight infection.

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Opsonins

Proteins that coat pathogens, making them more easily recognized and engulfed by phagocytic cells.

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Natural Killer (NK) Cells

Immune cells that recognize and destroy virus-infected or cancerous cells.

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Phagocytes

Immune cells that engulf and destroy pathogens

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Host Defenses

The body's various mechanisms to prevent infection. Can be physical, chemical, or cellular.

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MHC

Major Histocompatibility Complex; a group of genes that code for cell surface proteins responsible for presenting antigens to T cells.

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CD4+ Helper T Cells

T cells that express the CD4 protein and recognize antigens presented by MHC class II molecules. They are involved in coordinating immune responses.

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CD8+ Cytotoxic T Cells

T cells that express the CD8 protein and recognize antigens presented by MHC class I molecules. They kill infected or cancerous cells.

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Class I vs. Class II MHC

Class I MHC is found on all nucleated cells and presents antigens to CD8+ T cells. Class II MHC is found on antigen-presenting cells and presents antigens to CD4+ T cells.

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Antigen-Specific T and B Cells

Immune cells with unique receptors that recognize specific antigens. They are rare in the body but expand rapidly upon encountering the antigen.

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Co-stimulation

A second signal required for T cell activation, provided by 'costimulatory molecules' on antigen-presenting cells. This helps prevent T cell responses to harmless antigens.

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Clonal Expansion

The rapid proliferation of antigen-specific T or B cells after encountering their specific antigen. This creates a large army of cells to fight the infection.

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Dendritic Cells

Antigen-presenting cells that specialize in capturing antigens in tissues and displaying them to T cells in lymph nodes.

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Antigen

A molecule recognized by the immune system, usually a protein, that stimulates an immune response.

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Epitope

The specific part of an antigen that is recognized and bound by an antibody or T cell receptor.

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What do B cell receptors (BCRs) do?

BCRs recognize and bind specific antigens, similar to how antibodies do.

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What is the role of T cells in antigen recognition?

T cells recognize antigens presented by antigen-presenting cells (APCs). This presentation is done via MHC molecules.

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What are the key effector functions of Th1 cells?

Th1 cells help activate macrophages and CD8+ T cells to kill intracellular pathogens.

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What are the key effector functions of Th2 cells?

Th2 cells promote antibody production by B cells, specifically targeting extracellular pathogens.

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What is immunological memory?

The ability of the immune system to remember a pathogen and mount a faster, more efficient response upon re-exposure.

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What is the structure of an antibody?

Antibodies are Y-shaped proteins with two antigen-binding sites and a constant region for effector functions.

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Antibody Structure

Antibodies are made of two heavy and two light chains, forming two antigen-binding sites (Fab) and a constant region (Fc) responsible for effector functions like complement activation and Fc receptor binding.

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What do Antibodies do?

Antibodies neutralize pathogens by binding to them, preventing them from infecting cells. They also enhance phagocytosis (engulfment by immune cells) and can activate the complement system to kill pathogens.

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T cell Receptor (TCR)

T cells express TCRs on their surface, which recognize specific antigens presented by MHC molecules on other cells.

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Types of T cells

T cells differentiate into different types: cytotoxic T cells (CD8+) kill infected cells, helper T cells (CD4+) help B cells and other immune cells, and regulatory T cells (usually CD4+) suppress immune responses.

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Antigen Recognition by T and B cells

B cells directly recognize antigens in their free form or on microbes. T cells cannot recognize free antigens and need them presented by MHC molecules on antigen-presenting cells.

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What are MHC molecules?

MHC molecules are cell surface proteins that present antigens to T cells. Class I MHC presents antigens to CD8+ T cells, and Class II MHC presents antigens to CD4+ T cells.

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Immunological Tolerance

A state where the immune system does not attack the body's own cells and tissues (self-antigens).

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Central Tolerance

The process of eliminating self-reactive immune cells during their development in the bone marrow (for B cells) or thymus (for T cells).

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Peripheral Tolerance

Mechanisms that prevent self-reactive immune cells from causing harm after they have matured and entered the body.

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Anergy

A state of unresponsiveness where immune cells become inactive and unable to mount a response to a specific antigen.

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How is diversity in antigen receptors generated?

During lymphocyte development, segments of the genes encoding antigen receptors undergo random recombination, creating millions of different receptor variants.

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What happens to self-reactive lymphocytes?

They are removed during development to prevent autoimmune reactions. This ensures the immune system focuses on attacking foreign invaders.

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Immunotherapy

A type of treatment that uses the immune system to fight diseases, such as cancer and autoimmune disorders.

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What are some ways immunotherapy can be used?

Immunotherapy can be used to boost the immune system's attack on cancer cells, suppress autoimmune reactions, or replace missing or dysfunctional immune components.

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Apoptosis

Programmed cell death, a normal process where cells self-destruct in a controlled manner to eliminate damaged or unwanted cells, like self-reactive T cells in the thymus.

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Active Suppression

A process where regulatory T cells (Tregs) suppress the activity of other immune cells, preventing them from attacking self-antigens or causing unnecessary immune responses.

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Tolerogenic Antigen Presentation

A way of presenting antigens to immune cells that leads to tolerance instead of activation of an immune response. This can be achieved by using specific cells or signals.

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Inhibitory Ligands

Molecules that bind to receptors on immune cells, sending a signal to suppress or inhibit their activity, like lowering the immune response.

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Autoimmunity

Immune system mistakenly attacking the body's own tissues and cells, leading to diseases like rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, and psoriasis.

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Tumor Immune Evasion

Strategies used by tumor cells to evade the immune system, avoiding detection and destruction by immune cells.

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Checkpoint Inhibitors

Drugs that block the interaction of checkpoint molecules, like PD-L1 and PD-1, on immune cells, allowing the immune system to fight cancer more effectively.

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CAR T-Cell Therapy

A therapy that uses a patient's own T cells, genetically modified to express a chimeric antigen receptor (CAR) that targets specific proteins on leukemia cells, effectively killing them.

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PD-L1/PD-1 Inhibitors

Drugs that block the interaction between PD-L1 (on tumor cells) and PD-1 (on immune cells), releasing the brakes on the immune system's anti-tumor response, allowing it to fight cancer more effectively.

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Monoclonal Antibodies

Antibodies specifically targeting a single antigen, used to treat various diseases by neutralizing harmful substances like cytokines or blocking cell receptors.

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TNFα

A powerful pro-inflammatory cytokine that promotes inflammation. It is targeted by drugs (e.g., Adalimumab) to treat inflammatory conditions like rheumatoid arthritis and Crohn's disease.

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Chimeric Antigen Receptor (CAR)

A genetically engineered receptor protein inserted into T cells, enabling them to recognize and attack specific antigens on targeted cells, like cancer cells.

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Study Notes

Innate Immune System

  • The innate immune system is a first line of defense against pathogens, acting quickly to limit infection.
  • It comprises physical and chemical barriers, cellular mediators (e.g., macrophages, neutrophils, dendritic cells, mast cells, T cells, B cells) and soluble mediators (e.g., cytokines, complement proteins, acute phase proteins).
  • Learning outcomes include understanding complement system activation and its key functions, the role of opsonins in host defense, the role of acute phase proteins, and the functionality of Natural Killer (NK) cells against infected cells.

Host Barriers to Infection

  • Physical/chemical barriers prevent pathogen entry (e.g., skin, mucus membranes).
  • Phagocytes engulf and destroy pathogens.
  • Cytokines regulate immune responses by directing cell migration.

Properties and Functions of Extracellular Innate Mediators

  • Various soluble mediators are part of the innate immune system.
  • Some mediators are present constantly (constitutive), while others are produced in response to infection (inducible).
  • Mediators directly kill pathogens or mark them for phagocytosis (opsonisation).
  • Mediators also recruit immune cells and activate immune cells/systemic inflammatory reactions.

Opsonins and Opsonisation

  • Opsonisation is the coating of a pathogen with opsonins, making it easier for phagocytes to recognise and engulf it.
  • Opsonins include antibodies and complement proteins.
  • Phagocytes possess specific receptors for opsonins.

Cytokines

  • Cytokines are small proteins mediating communication within the immune system.
  • Cytokines play critical roles in regulating the type, magnitude, and location of immune responses.

Chemokines and Cell Migration

  • Chemokines are a group of cytokines directing immune cell migration (chemotaxis) towards the source of the chemokine.
  • Cell response to chemokines depends on chemokine receptor expression on the cell surface.

Acute Phase Proteins

  • Synthesized in the liver in response to inflammation (inducible).
  • Sentinel cells release cytokines (e.g., IL-6), stimulating acute phase protein production.
  • Functions include: immune cell recruitment, pattern recognition (bacterial/fungal polysaccharides/glycolipids), and activation of the complement cascade. They also bind to and kill pathogens, enhancing uptake by phagocytic cells (opsonisation).
  • Acute phase proteins are used as non-specific indicators of infection/inflammation.

Complement System

  • The complement system is a cascade of proteins that enhance immune responses and destroy pathogens.
  • It may be activated through three pathways (classical – antibody, alternative – direct contact, lectin – carbohydrates).
  • Each pathway initiates a cascade resulting in a C3 convertase that cleaves C3 into opsonin C3b and anaphylatoxin C3a.
  • These actions increase vasodilation, vascular permeability, recruit immune cells, and enhance pathogen degradation by phagocytes.

Complement Activation

  • Complement systems can be activated via the classical, alternative, or lectin pathways.
  • They initiate with the recognition of the pathogen surface.
  • Complement activation leads to the creation of membrane attack complex (MAC), which creates pores in pathogen membranes causing lysis.

C3 Cleavage

  • All complement activation pathways trigger a cascade resulting in C3 convertase.
  • Cleaving C3 leads to the generation of opsonin C3b and anaphylatoxin C3a.
  • This promotes vasodilation, vascular permeability, immune cell recruitment and pathogen degradation by phagocytes.

C5a and the Membrane Attack Complex (MAC)

  • C5 convertase cleaves C5 to C5a and C5b.
  • C5a is an anaphylatoxin increasing vascular permeability and expression of adhesion molecules.
  • C5b initiates the formation of the MAC, which creates pores in the target cell membrane triggering lysis.

Anti-viral Defences

  • Key processes, such as interferons (viral response), and NK cells in identifying and eliminating stressed or infected cells. Type 1 interferons are produced by infected cells; they act on neighbouring cells to increase resistance to viral infection, and also act to enhance MHC-I expression and antigen presentation.

Natural Killer (NK) Cells

  • NK cells are important for recognizing and killing stressed cells, such as virally infected or cancerous cells.
  • These cells lack antigen-specific receptors.
  • NK cells make up around 10% of peripheral lymphocytes.

Next Steps

  • Adaptive immune system will be studied.

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Related Documents

PL1003 - Topic 4 - Lecture 4.4 - Tolerance and Immunotherapy Lecture Notes PDF
Innate Immunity Lecture Slides PDF
PL1003 Topic 4 Lecture 4.3 Adaptive Immune Response PDF

Description

This quiz focuses on the innate immune system, its components, and functions. It explores the role of physical and chemical barriers, cellular mediators, and soluble mediators in host defense. Understanding the activation of the complement system, opsonins, and the functionality of Natural Killer (NK) cells is essential for grasping the innate immune response.

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