Podcast
Questions and Answers
What is the primary function of the adaptive immune system?
What is the primary function of the adaptive immune system?
- To maintain memory cells for faster response to reinfections (correct)
- To produce cytokines and chemokines
- To control pathogen replication
- To provide immediate response to all pathogens
The innate immune system continues to function actively even after the pathogen clearance.
The innate immune system continues to function actively even after the pathogen clearance.
False (B)
What are the two types of mechanisms by which immune cells contribute to killing pathogens?
What are the two types of mechanisms by which immune cells contribute to killing pathogens?
Direct cytotoxicity and indirect communication
The immune system resolves inflammation and returns to __________.
The immune system resolves inflammation and returns to __________.
Match the following components of the immune system with their descriptions:
Match the following components of the immune system with their descriptions:
What is the primary function of cDC1 cells?
What is the primary function of cDC1 cells?
Plasmacytoid dendritic cells are the most numerous DC subset found in epithelium and lymphoid organs.
Plasmacytoid dendritic cells are the most numerous DC subset found in epithelium and lymphoid organs.
What are the cytoplasmic organelles found in Langerhans cells called?
What are the cytoplasmic organelles found in Langerhans cells called?
CDC2 cells are involved in activating CD4+ T cells and orchestrating a broader immune response, including Th1, Th2, and Th______.
CDC2 cells are involved in activating CD4+ T cells and orchestrating a broader immune response, including Th1, Th2, and Th______.
Match the following types of dendritic cells with their primary functions:
Match the following types of dendritic cells with their primary functions:
What is the primary role of ILC1/NK cells?
What is the primary role of ILC1/NK cells?
ILC2 cells contribute to tissue repair by secreting amphiregulin.
ILC2 cells contribute to tissue repair by secreting amphiregulin.
What cytokines do ILC3 cells primarily produce?
What cytokines do ILC3 cells primarily produce?
ILC3 cells maintain intestinal homeostasis by regulating the balance between __________ to commensal bacteria and defense against pathogenic organisms.
ILC3 cells maintain intestinal homeostasis by regulating the balance between __________ to commensal bacteria and defense against pathogenic organisms.
Match the ILC type with its primary transcription factor:
Match the ILC type with its primary transcription factor:
What is an outcome of overactive ILCs?
What is an outcome of overactive ILCs?
ILC2 cells play a role in responding to parasitic infections by secreting IL-5 and IL-13.
ILC2 cells play a role in responding to parasitic infections by secreting IL-5 and IL-13.
Identify the common lymphoid progenitors that primarily give rise to ILC2 and ILC3.
Identify the common lymphoid progenitors that primarily give rise to ILC2 and ILC3.
ILC1 activation is primarily triggered by __________, IL-18 and IL-15.
ILC1 activation is primarily triggered by __________, IL-18 and IL-15.
What is the primary function of IL-25 and IL-33 in relation to ILC2 cells?
What is the primary function of IL-25 and IL-33 in relation to ILC2 cells?
Which type of dendritic cell is specialized in antigen presentation and T cell activation?
Which type of dendritic cell is specialized in antigen presentation and T cell activation?
Follicular dendritic cells present protein antigens to T cells.
Follicular dendritic cells present protein antigens to T cells.
What key role do plasmacytoid dendritic cells play in the immune response?
What key role do plasmacytoid dendritic cells play in the immune response?
Immature DCs located in peripheral tissues are specialized for _______.
Immature DCs located in peripheral tissues are specialized for _______.
Match the following dendritic cell types with their primary characteristics:
Match the following dendritic cell types with their primary characteristics:
Which surface marker is associated with plasmacytoid dendritic cells?
Which surface marker is associated with plasmacytoid dendritic cells?
DCs have a low phagocytic activity when immature.
DCs have a low phagocytic activity when immature.
What are the two main lineages from which conventional dendritic cells develop?
What are the two main lineages from which conventional dendritic cells develop?
The primary function of CD11c, a marker found on cDCs, is the _______.
The primary function of CD11c, a marker found on cDCs, is the _______.
Which cytokine is primarily produced by cDC2s?
Which cytokine is primarily produced by cDC2s?
What is the primary function of MHC molecules?
What is the primary function of MHC molecules?
MHC class II molecules present intracellular antigens to T cells.
MHC class II molecules present intracellular antigens to T cells.
What are the three types of MHC molecules?
What are the three types of MHC molecules?
MHC genes are located on chromosome ______.
MHC genes are located on chromosome ______.
Match the following MHC molecules with their corresponding characteristics:
Match the following MHC molecules with their corresponding characteristics:
Which MHC class is primarily recognized by CD8+ cytotoxic T cells?
Which MHC class is primarily recognized by CD8+ cytotoxic T cells?
HLA-B27 is associated with ankylosing spondylitis.
HLA-B27 is associated with ankylosing spondylitis.
What is meant by 'balancing selection' in the context of MHC genes?
What is meant by 'balancing selection' in the context of MHC genes?
MHC class I molecules are present on ______ nucleated cells.
MHC class I molecules are present on ______ nucleated cells.
Match the following MHC genes with their respective classes:
Match the following MHC genes with their respective classes:
What does the peptide-binding groove of MHC class II allow?
What does the peptide-binding groove of MHC class II allow?
MHC molecules have minimal genetic diversity among individuals.
MHC molecules have minimal genetic diversity among individuals.
Name one function of MHC class III molecules.
Name one function of MHC class III molecules.
MHC molecules are crucial for distinguishing ______ from non-self.
MHC molecules are crucial for distinguishing ______ from non-self.
Study Notes
Innate vs Adaptive Immunity
- The innate immune system responds quickly to a broad range of pathogens, controlling replication while stimulating the adaptive response. Adaptive immunity is slower but more specific and requires an initial response from the innate system to fully clear pathogens
- Memory cells are produced by the adaptive immune system, leading to more rapid and robust responses during reinfection
Immune Response Steps
- Recognition: Pathogens are recognized by receptors on immune cells.
- Activation: Immune cells change in response to infection.
- Effector Mechanisms: Effector mechanisms kill pathogens by directly killing or by releasing signaling molecules that indirectly influence other immune cells.
- Resolution: Inflammation is resolved and homeostasis is restored.
- Barrier Immunity: Mucosal barriers maintain homeostasis, regulate microbiota, and promote tissue repair.
Innate Lymphoid Cells (ILCs)
- ILC1/NK cells: Defend against intracellular pathogens by producing IFN-γ to activate macrophages and promote cytotoxic activity.
- ILC2: Respond to parasitic infections and allergens, contributing to type 2 immunity by secreting IL-5 and IL-13.
- ILC3: Defend against extracellular bacteria and fungi through the production of IL-7 and IL-22, maintaining epithelial integrity and stimulating antimicrobial peptide production.
ILC Role in Tissue Homeostasis and Repair
- ILC2: Contribute to tissue repair in the lungs and gut by secreting amphiregulin, promoting epithelial cell proliferation.
- ILC3: Maintain intestinal homeostasis by regulating tolerance to commensal bacteria and defense against pathogens.
ILC Contribution to Inflammation and Disease
- Overactive ILCs contribute to allergic diseases like asthma, atopic dermatitis, and chronic rhinosinusitis.
- ILC3s are linked to inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis.
ILC Development
- ILCs originate from common lymphoid progenitors (CLPs) in the bone marrow but branch off early due to their lack of recombination-activating gene (RAG)-dependent receptor rearrangement.
- Early innate lymphoid progenitor (EILP): Retains the capacity to differentiate into all ILCs, but not adaptive lymphocytes.
- Common helper-like innate lymphoid progenitor (CHILP): Gives rise to ILC2 and ILC3, but not NK cells or T cells.
Transcription Factors for ILC Development
- ILC1/NK cells: T-bet and Eomes (eomesodermin).
- ILC2: GATA3 and Rorα.
- ILC3: RORγt and AHR (aryl hydrocarbon receptor).
ILC Activation
- ILCs are maintained in a quiescent state under normal conditions.
- Local cues, such as damage-associated molecular patterns (DAMPs) or cytokines (IL-25, IL-33) activate ILCs, resulting in proliferation and the release of effector cytokines that shape the immune response.
Activation Signals for ILC Types
- ILC1: IL-12, IL-18 and IL-15, stress ligands (e.g., MIC-A/MIC-B for NK cells).
- ILC2: IL-25, IL-33, TSLP, IL-4.
- ILC3: IL-1β, IL-23, IL-7.
Regulatory Inputs for ILC Activation
- Classical/conventional dendritic cells (cDCs): The primary DC subset, involved in capturing protein antigens from microbes and presenting them to T cells.
- cDC1: Specializes in cross-presentation of antigens to CD8+ T cells, essential for anti-viral and anti-tumor immunity.
- cDC2: Activates CD4+ T cells (helper T cells) and orchestrates a broader immune response (both Th1, Th2, and Th17 pathways).
- Plasmacytoid dendritic cells (pDCs): Resemble plasma cells, and are the main producers of type I interferons. Play a crucial role in antiviral immunity.
- Monocyte-derived dendritic cells (moDCs): Differentiate from monocytes in inflammatory conditions, playing a significant role in inflammation and infection.
- Langerhans cells: Found in the epidermis, function in the context of skin infections to activate CD4+ T cells or induce tolerance to self-antigens.
- Follicular DCs: Do not present protein antigens, but are involved in B cell activation in lymph nodes.
MHC Molecules
- MHC class I: Presents intracellular antigens to CD8+ cytotoxic T cells, which can kill infected or malignant cells. Found on most nucleated cells.
- MHC class II: Presents extracellular antigens to CD4+ helper T cells.
- MHC class III: Encodes immune-related proteins such as complement proteins and cytokines.
MHC Genes
- MHC genes are located in the human leukocyte antigen (HLA) complex on chromosome 6.
- MHC genes are highly polymorphic, contributing to genetic diversity in the population.
- The different alleles are inherited in haplotypes, resulting in a diverse set of antigen-presenting capabilities in each individual.
- Polymorphism in MHC genes allows for recognition of a broad range of antigens, enhancing the ability to respond to diverse pathogens.
MHC Genes and Disease Association
- HLA-B27 is associated with ankylosing spondylitis.
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Description
Test your knowledge on the differences between innate and adaptive immunity. This quiz covers the immune response steps, the role of memory cells, and the functions of innate lymphoid cells. Understand how the immune system protects the body from pathogens and restores homeostasis.
