Innate and Adaptive Immunity Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary characteristic of innate defenses?

They primarily depend on B and T lymphocytes.

They involve cells and molecules present at all times. (correct)

They are activated after days of infection.

They can distinguish between different types of pathogens.

Which statement best describes the role of mechanical and chemical defenses in immune response?

They are part of adaptive immunity.

They require activation for full effectiveness.

They serve as the first line of defense against pathogens. (correct)

They are less effective than adaptive immunity.

What distinguishes innate immunity from adaptive immunity?

Innate immunity can adapt to various pathogens.

Adaptive immunity acts within minutes of infection.

Adaptive immunity provides immediate response.

Innate immunity is present continuously. (correct)

What happens if pathogens are not cleared by the innate immune system?

They are handled by the adaptive immune system. Signup and view all the answers

How quickly can innate defenses be activated following an infection?

Within hours to minutes after infection. Signup and view all the answers

Which layer of immune defense provides a rapid deployment force against pathogens?

Innate immunity Signup and view all the answers

What is a limitation of innate immunity?

It has a limited ability to distinguish between pathogens. Signup and view all the answers

What is the time frame for the full activation of adaptive immunity?

Days after the initial exposure. Signup and view all the answers

What role do chemical defenses play in the immune system?

They prevent infection by acting as a first line of defense. Signup and view all the answers

What is the main function of lymph nodes in the immune system?

To filter lymphatic fluid and initiate adaptive immune responses. Signup and view all the answers

Which cell types are primarily involved in the adaptive immune response?

T-cells and B-cells. Signup and view all the answers

The lymphatic system is responsible for returning fluid to which part of the body?

The circulatory system. Signup and view all the answers

Which component is crucial for bridging the innate and adaptive immune responses?

The complement system. Signup and view all the answers

What is the primary role of antigen-laden dendritic cells in the immune response?

They present antigens to T cells. Signup and view all the answers

What is the relationship between innate immunity and adaptive immunity?

Innate immunity provides immediate defense while adaptive immunity provides long-term protection. Signup and view all the answers

Where do T cells exit the lymph node?

Through efferent lymphatic vessels. Signup and view all the answers

After interacting productively with T cells, what do B cells do?

They move into follicles and differentiate into plasma cells. Signup and view all the answers

What is primarily filtered by lymph nodes as part of their immune function?

Pathogens and foreign particles from lymphatic fluid. Signup and view all the answers

Which part of the immune system is mainly targeted by the adaptive immune response?

Specific antigens presented by pathogens. Signup and view all the answers

How long does a typical circulation cycle for T and B cells take?

12-24 hours Signup and view all the answers

What is the primary function of the thoracic duct?

To return lymph to the circulation. Signup and view all the answers

What is the role of C1q in the complement system?

It organizes the C1 complex. Signup and view all the answers

How does C3b function in the immune response?

It labels pathogens for phagocytosis. Signup and view all the answers

Which component of the C1 complex is responsible for cleaving molecules of C3?

C1s Signup and view all the answers

What structural feature is characteristic of C1q?

It possesses long collagen-like tails. Signup and view all the answers

Which statement accurately describes C1q's composition?

It is made up of six identical globular heads. Signup and view all the answers

What is implied by the presence of the C1 complex?

It is the initial trigger for the classical complement pathway. Signup and view all the answers

What role do opsonins play in the immune system?

They facilitate the recognition of pathogens by phagocytes. Signup and view all the answers

Which of the following best describes the action of C3 in the complement cascade?

It enhances the opsonization of pathogens. Signup and view all the answers

What is the primary function of C3b in the complement system?

To serve as an opsonin Signup and view all the answers

What does the cleavage of C4 by activated C1s produce?

C4a and C4b Signup and view all the answers

Which of the following statements is true regarding C4a?

C4a acts as an anaphylatoxin Signup and view all the answers

Which molecule acts as C5 convertase in the complement pathway?

C4b.2b.3b Signup and view all the answers

What role does C5b play in the complement system?

It recruits additional complement proteins Signup and view all the answers

Which pairs of molecules are involved in the initial recognition of antigens in the classical pathway?

IgM and C1 Signup and view all the answers

How does C1s become activated in the complement cascade?

Through the presence of antigens Signup and view all the answers

Which of the following components is released as a byproduct during the cleavage of C5?

C5a Signup and view all the answers

What is the ultimate outcome of the complement cascade?

Formation of the membrane attack complex Signup and view all the answers

What is the initial processing step in the classical complement pathway?

C1s cleaving C4 Signup and view all the answers

What is the primary function of the membrane attack complex (MAC) composed of complement proteins C5b-C9?

To create pores in the membranes of pathogens Signup and view all the answers

How does the mannose-binding lectin (MBL) bind to carbohydrates?

Only to mannose residues with correct spacing Signup and view all the answers

Which receptor enhances the detection of pathogens by phagocytes when bound with antibodies?

Fc receptor Signup and view all the answers

What similarity do the MBL pathway and the classical pathway share?

They both form a complex with serine proteases Signup and view all the answers

What type of residues does MBL specifically bind to?

Carbohydrates with specific spacing like mannose and fucose Signup and view all the answers

What enhances the ability of phagocytes to recognize and engulf pathogens?

Cooperation between Fc and complement receptors Signup and view all the answers

How does the spacing of mannose and fucose residues affect MBL binding?

Only correct spacing of residues allows MBL to bind effectively Signup and view all the answers

What component of the complement system forms the membrane attack complex?

C5b fragment Signup and view all the answers

Study Notes

Innate Immunity

Vertebrate immune defenses have three layers
- Mechanical/chemical defenses: Epithelia and skin, low pH gastric environment, antibacterial enzymes
- Innate immunity: Phagocytic cells (neutrophils, dendritic cells, macrophages), natural killer (NK) cells, complement proteins, interleukins (IL-1, IL-6)
  - Rapid activation (minutes to hours)
  - Limited ability to distinguish between pathogens
- Adaptive immunity: B and T lymphocytes
  - Requires days for full activation
  - Enhanced by innate immune response products
  - Antibodies facilitate innate immunity

Lymphatic System

Network of conduits carrying lymph
Lymph nodes: Filter lymph, mature white blood cells (500-600 in humans)
Lymph vessels: Convey lymph
Thoracic duct: Discharges lymph into blood
Bone marrow: B cell development, T cell precursors
Thymus: T cell maturation
Spleen: Lymphocyte maturation, filters lymph

Adaptive Immune Response in Lymph Nodes

Lymph nodes filter fluid returning to major collecting ducts.
Antigens are carried in two forms:
- Soluble antigens
- Antigen-laden dendritic cells
Soluble antigens bind to B cells.
Antigen-laden dendritic cells activate T cells.
Interactions between T and B cells lead to B cell differentiation.
Plasma cells produce antibodies.
Lymphocytes recirculate between lymph and blood (12-24 hours).

Dendritic Cells as Links

Activated dendritic cells migrate to the infection site via blood.
Dendritic cells carry microbial peptides to lymph nodes.
Activated dendritic cells activate T cells with appropriate receptors.

Complement System

Heat-sensitive plasma component enhancing opsonization & killing of bacteria.
Many plasma proteins interacting to opsonize pathogens.
Induces inflammatory responses to fight infection.
Three pathways (classical, lectin, alternative) activate complement proteins via proteolytic cleavage.
Classical pathway: Activated by antigen-antibody complexes, C1 (C1q, C1r, C1s) binds to the antibody constant region or directly to pathogen surface. This causes a conformational change, activating C1s (serine protease)
Lectin pathway: Activated by mannose-binding lectin (MBL) binding to pathogen surfaces.
Alternative pathway: Activated by pathogen surfaces. Factor B binds to C3b, Factor D cleaves factor B into Bb and Ba, forming C3 convertase (C3bBb). Complement proteins act as opsonins (to tag) and inflammatory mediators (C3a, C4a, C5a)

Complement Activation (Classical Pathway)

C1s cleaves C4 to C4a+ C4b; C4b binds to pathogen surface.
C1s cleaves C2 to C2a + C2b; C4b binds C2b = C3 convertase (C4b2b).
C3 convertase cleaves C3 to C3a+ C3b; C3b is an opsonin that binds to the microbial surface or to the convertase.
C3b binds to C4b2b = C5 convertase.
C5 convertase cleaves C5 to C5a +C5b. C5b initiates the formation of the membrane attack complex (MAC).
C5b recruits C6, C7, C8-C9 proteins into membrane-bound pores to cause cytolysis.
Complement proteins enhance phagocytosis.

Antibody Structure and Digestion

Immunoglobulins are globular proteins with heavy and light chains.
Five classes (IgA, IgD, IgE, IgG, IgM).
Light chains are 2 types (κ and λ).
Heavy chains define isotype.
Constant regions vary by isotype.
Papain digestion cleaves IgG into two F(ab) fragments and one Fc fragment.
Pepsin digestion cleaves IgG into one F(ab')2 fragment and one Fc fragment degraded
F(ab) is monovalent (one antigen binding site)
F(ab')2 is bivalent (two antigen binding sites).
Immunoglobulin isotypes vary in structure of Fc and other elements.

Transcytosis of IgA and IgG

IgA & IgG transported across epithelia
- IgA binds to the polymeric IgA receptor (pIgR) and is endocytosed.
- pIgR transports IgA across epithelium releasing the secretory IgA piece and the antibody.

Immunological Memory (Primary and Secondary Responses)

Primary response: Mostly IgM, some IgG.
Secondary response: Faster and greater response, mostly IgG, some IgM, IgA, IgE.
Memory to antigen A during second immunization
Secondary response is specific to antigen A.
Antibodies in secondary response bind with tighter affinity to antigen.

VDJ Recombination

This mechanism randomly assembles genes coding for specific immune proteins.
RAG1 and RAG2 enzymes are involved to recognize and induce DNA cleavage at recombination signal sequences (RSS).
V, D, and J segments combine to create a unique variable domain in immunoglobulin.

Antibody Diversity

V, D, and J segments are rearranged randomly in the heavy chain variable region.
Similar rearrangements occur in the light chain variable region (V and J segments).

Antibody Structure

Antibodies consist of heavy and light chains linked by disulfide bonds.
V(Variable) segments account for variability in antigen binding.
C(Constant) segments define isotypes and effector functions.

Immunoglobulin Isotypes

Five isotypes (IgM, IgD, IgG, IgA, IgE).
IgM is usually produced first in response to a pathogen.

Classes of Immunoglobulins

IgM, IgD : Monomers
IgA: Dimer
IgG: Monomer
IgE: Monomer

Structure of T-cell Receptor (TCR)

TCR is a heterodimer (α and β chains).
Associates with CD3 complex for signal transduction.
Interacts with co-receptors (CD4 or CD8) for MHC binding.

Signal Transduction from TCR and BCR

Src kinases (Lck, Fyn, Lyn) phosphorylate ITAMs.
ITAMs recruit non-Src kinases (ZAP-70, Syk)
Activated kinases activate various downstream signalling molecules.

Class I and Class II MHC Proteins

Class I MHC proteins are expressed on most nucleated cells (not RBCs).
MHC class I associated with ß2-microglobulin, presents peptides from intracellular proteins (e.g., virally-infected cells).
Class II MHC are expressed primarily by professional APCs (dendritic cells, macrophages, B cells).
MHC class II present peptides from extracellular proteins.
An individual has many different MHC alleles providing variability in peptide presentation.

Cytokines in T-cell Activation

IL-2, IL-4 and IL-7 influence CD4+ T-cell differentiation
IL-12 & IFNγ influence CD4+ T-cells into TH1 cells.

Cytotoxic T Cells (CTLs)

CTLs recognize viral peptides presented by class I MHC.
Release perforins and granzymes to induce target cell death.

Activation of B Cells

Three signals required for B-cell activation.
- Antigen recognition by BCR.
- CD40L on TH cell binds to CD40 receptor.
- Cytokines stimulate B cell responses.

Positive Selection of T Cells

Thymocytes that bind to self-MHC survive.
Thymocytes binding to foreign antigens die or are rejected via apoptosis.

Negative Selection of T Cells

Thymocytes recognizing self-antigens are eliminated or undergo receptor editing.
- Prevents autoimmune reactions.

MHC Proteins and Viral Infections

Viruses can evade CTL destruction by suppressing MHC class I expression, making the infected cells a target for NK cells.
NK cells have activating receptors that target infected or cancer cells.
Inhibitory receptors recognise MHC-I molecules on healthy cells.

Toll-like Receptors (TLRs)

TLRs recognize pathogen-associated molecular patterns (PAMPs).
Initiate innate immune system activation.

Antigen Cross Presentation

Some antigen presenting cells (APCs) can present extracellular antigens on MHC class I to CD8 T cells.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the characteristics and functions of innate and adaptive immunity. This quiz covers key concepts like protective mechanisms, the roles of various immune cells, and the differences between innate and adaptive responses. Perfect for students studying immunology or biology!