Immune System Microbial Detection Quiz

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Questions and Answers

Which type of immunity involves the immediate response to pathogens via cells such as neutrophils and macrophages?

Humoral Immunity

Cell-mediated Immunity

Innate Immunity (correct)

Adaptive Immunity

What is the role of pattern recognition receptors (PRRs) in the immune system?

They create antibodies against specific antigens.

They recognize conserved patterns on pathogens. (correct)

They increase blood flow to the infection site.

They eliminate pathogens directly.

During an inflammatory response, which process helps increase the permeability of local blood vessels?

Chemotaxis

Phagocytosis

Vasodilation (correct)

Vasoconstriction

Which of the following statements about cytokine signaling is true?

Cytokines can facilitate communication between immune cells. Signup and view all the answers

How do some microbes evade detection by the immune system?

By mimicking host tissues or avoiding immune responses. Signup and view all the answers

What is the role of NF-κB in the immune response to bacterial infections?

It activates intracellular pathways leading to gene transcription. Signup and view all the answers

Which of the following mechanisms do some pathogens employ to evade the immune response?

Degrading NF-κB and its activators. Signup and view all the answers

How do dendritic cells contribute to the adaptive immune response?

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

What is a key function of Caspase-1 in the context of inflammation?

It activates pro-inflammatory cytokines like IL-1β and IL-18. Signup and view all the answers

What is the impact of Influenza virus on the immune response?

It reduces anti-viral immune response by inhibiting PRRs. Signup and view all the answers

Which component of the immune system is primarily responsible for antibody production?

B cells. Signup and view all the answers

What do PAMPS and DAMPS represent in the immune response?

Pathogen-associated and damage-associated molecular patterns. Signup and view all the answers

Which of the following statements about the role of MyD88 is true?

MyD88 is part of the TLR signaling pathway to activate NF-κB. Signup and view all the answers

What happens when the immune system is activated at the wrong time?

It can cause allergies and autoimmunity. Signup and view all the answers

In the context of inflammation, what role does IL-1β play?

It is involved in promoting inflammatory responses. Signup and view all the answers

What do PAMPs stand for in the context of immune response?

Pathogen-Associated Molecular Patterns Signup and view all the answers

How does the Danger Model proposed by Polly Matzinger differ from traditional views of immune response?

It focuses on damage or danger signals instead of just non-self antigens. Signup and view all the answers

Which of the following is an example of a DAMP?

Nuclear proteins released from dying cells Signup and view all the answers

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

To engulf pathogens and present antigens to adaptive immune cells. Signup and view all the answers

Which complement protein is essential for the formation of the membrane attack complex (MAC)?

C9 Signup and view all the answers

What is the main function of opsonization in the immune response?

To improve phagocytosis of pathogens. Signup and view all the answers

Which of the following is NOT typically recognized by Pattern Recognition Receptors (PRRs)?

Nutrients from host cells Signup and view all the answers

What function do cytokines released by immune cells serve?

They facilitate communication between immune cells. Signup and view all the answers

Which immune cell is primarily responsible for killing infected cells?

CD8+ T cell Signup and view all the answers

Which type of receptor primarily recognizes carbohydrates in pathogens?

C-type lectin-Like Receptors Signup and view all the answers

Which statement about complement evasion by pathogens is true?

Smallpox virus uses a protein to inactivate key complement components. Signup and view all the answers

How do macrophages contribute to the immune response?

They engulf pathogens and also activate adaptive immunity. Signup and view all the answers

What is the role of fibroblasts in the immune response?

To support the structure of tissues during immune activation. Signup and view all the answers

What type of immune cell is responsible for coordinating the immune response?

CD4+ T cell Signup and view all the answers

Study Notes

Immune System Danger Sensing

The immune system must distinguish between foreign, dangerous substances, and harmless or self substances.
Different microbes have characteristic molecules, enabling immune cells to recognise pathogens.
Key objectives include describing how microbes are detected by immune cells and methods microbes use to avoid detection.
Questions to consider:
- What microbial substances activate the immune system?
- How does the immune system recognise the damage caused by pathogens?
- Which cells and receptors respond to microbial products?
- What are the consequences of microbial sensing for the host?
- How do microbes evade detection?

Initial Infection Response

Local innate immune cells are activated.
Blood vessel permeability increases.
Migration of more immune cells and plasma proteins into tissues (acute inflammation).
Immune cells involved include dendritic cells, blood vessels, macrophages, neutrophils, and monocytes.

Host Receptors

Charles Janeway predicted host receptors recognizing conserved patterns on pathogenic molecules.
Key researchers include Janeway, Beutler, Hoffmann, and Steinman (Nobel Prize 2011).

PAMPs

PAMPs (Pathogen Associated Molecular Patterns) are microbial components differentiating microbes from host cells.
Examples of PAMPs include viral nucleic acids, bacterial DNA, fungal polysaccharides, and protozoan glycolipids..

Danger Model

Polly Matzinger argued the immune system senses danger, not just non-self.
The system responds to damage or danger, not just foreign antigens.

DAMPs

DAMPs (Damage-Associated Molecular Patterns) are molecules from dying cells.
Examples include nucleic acids and cytoplasmic proteins.

Information Transfer

Innate cells sense pathogens, and this information is passed to adaptive immune cells.
Adaptive immune cells include CD4+ T cells (coordinate immune response), CD8+ T cells (kill infected cells), and B cells (make antibodies to eliminate pathogens).

Leukocytes and Tissue Cells

Leukocytes (blood cells) and tissue cells (epithelial and fibroblast cells) detect and control pathogens at infection sites.
Immune cells, like dendritic cells and macrophages, engulf pathogens to activate adaptive immune cells.
Tissue cells, like epithelial cells, release inflammatory molecules.

Pathogen Avoidance of Complement

Host cells and some pathogens evade complement components.
Examples include CD46 inactivating C3b and CD59 stopping MAC formation.

Pattern Recognition Receptors (PRRs)

PRRs recognize PAMPs and DAMPs.
Different types of PRRs include Toll-like receptors (TLRs, mostly recognize PAMPs), Nucleotide-binding oligomerization domain-like receptors (NLRs), C-type lectin-like receptors (CLRs), and some other absent receptors.

PRR Location

PRRs are located on cell membranes (for bacteria and fungal recognition) or inside cells in the cytoplasm (for viral, bacterial, and DAMP/PAMP sensing).

Pathogen Hiding

Pathogens can hide from PRR recognition.
Examples include Helicobacter pylori flagellin, poliovirus RNA, and Listeria monocytogenes altered cell walls.

Consequences of PRR Activation

PRR activation leads to signaling to other cells, adaptive immune system activation, limiting microbe replication, and controlling pathogen presence.
The involved mechanisms include phagocytosis, inflammation, and cytokine release.

NF-κB Activation

Bacteria can alter gene transcription by activating NF-κB.
TLR activation initiates intra-cellular pathways activating NF-κB.
NF-κB activates gene transcription.

Pathogen Inhibition

Some pathogens limit NF-κB activation, reducing the warning signal to the immune system.
Examples include E. coli virulence factors and Shigella enzymes.

Inflammasomes

Some NLRs form inflammasomes.
Inflammasomes are platforms activating caspase-1.
Inflammasomes act in the cytoplasm of cells.

Viral Infection

Influenza virus infection causes inflammatory cytokines and cell death.
Influenza targets respiratory tract epithelial cells.
TLR and RIG-I signaling are involved.
Type I IFN is released reducing viral spread.

Viral Inhibition

Influenza virus inhibits intracellular activation of PRRs, reducing anti-viral immune responses.
NS1 inhibits NF-κB activation.

Adaptive Responses

Pathogens and the damage they cause trigger innate immune responses.
This sometimes activates adaptive immune responses (e.g., vaccination, immunity).
Pathogens can evade recognition, and sometimes, the immune response is inappropriately triggered (e.g., allergies, autoimmunity).

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Description

This quiz focuses on the immune system's ability to sense and respond to dangerous microbes. It covers the mechanisms by which immune cells identify pathogens and the strategies employed by microbes to evade detection. Explore key concepts about innate immune responses, cell activation, and the consequences for the host.