Innate Immunity and Complement System Quiz

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Questions and Answers

Which of these is a function of fever?

Increase alertness

Increase damage to the host

Slow the replication of bacteria and viruses (correct)

Increase the rate of bacterial and viral replication

Which of the following is an example of an endogenous inflammatory inducer?

Uric acid (correct)

Double-stranded RNA

Bee sting venom

Lipopolysaccharide

What role do pain and loss of function play in the inflammatory response?

They act as endogenous inflammatory inducers

They have no functional role

They act to prevent further damage by alerting the host to a problem (correct)

They directly cause further damage to the host

Which of the following is an exogenous inflammatory inducer?

Alum (C) Signup and view all the answers

Which of these cytokines plays a key role as a mediator of inflammation?

Interleukin-1 beta (IL-1 beta) (A) Signup and view all the answers

Which of the following best describes the primary function of Major Histocompatibility Complex (MHC) proteins?

To distinguish between self and non-self cells. (A) Signup and view all the answers

What is the main role of Natural Killer (NK) cells in the innate immune response?

To directly kill cells that lack MHC class I molecules. (C) Signup and view all the answers

How does the alternative pathway of complement activation differentiate between self and non-self cells?

By relying on the spontaneous cleavage of C3 and the presence of inhibitory proteins on self cells. (D) Signup and view all the answers

What is the main function of the membrane attack complex (MAC) in the complement system?

To directly kill cells by creating pores in their membranes. (C) Signup and view all the answers

What is the significance of the inhibitory receptors on Natural Killer (NK) cells?

They prevent NK cells from mistakenly killing healthy cells by recognizing MHC class I proteins. (A) Signup and view all the answers

Which of the following is NOT a primary function of inflammation?

To activate the adaptive immune system. (B) Signup and view all the answers

What is the role of C3 convertase in the alternative pathway of complement activation?

To cleave C3 into C3a and C3b. (C) Signup and view all the answers

How does a virally infected cell become susceptible to Natural Killer (NK) cell attack?

By downregulating the expression of MHC class I proteins. (B) Signup and view all the answers

What is the main function of Decay-Accelerating Factor (DAF) and Complement Receptor 1 (CR1) in the context of the alternative pathway?

To promote the dissociation of C3 convertases on the surface of self cells. (C) Signup and view all the answers

How do stressed or cancerous cells become targets for Natural Killer cells?

By upregulating activating ligands, and downregulating inhibitory ligands. (D) Signup and view all the answers

Which of the following is a characteristic of the alternative pathway of complement activation?

It involves the spontaneous activation of C3 in the blood. (B) Signup and view all the answers

What is a key function of opsonization by the complement system?

To mark pathogens for destruction by phagocytes. (B) Signup and view all the answers

Which component of the immune system is responsible for recognizing 'missing self' in the context of cell destruction?

Natural Killer (NK) cells. (D) Signup and view all the answers

Which of the following is a consequence of a genetic deficiency in Decay-Accelerating Factor (DAF)?

Embryonic lethality due to a failure in the self-recognition pathways. (B) Signup and view all the answers

Which characteristic differentiates the innate immune system from the adaptive immune system?

The innate recognizes self from non-self using pre-existing mechanisms, the adaptive does not. (D) Signup and view all the answers

Study Notes

Innate Immunity

Self-Nonself Discrimination: The immune system (IS) distinguishes between "self" (body's own cells) and "non-self" (invading organisms).
Natural Killer (NK) Cells: A type of innate lymphoid cell that recognizes and destroys infected, stressed, or cancerous cells. They have inhibitory and activating receptors; a healthy cell is recognized by the inhibitory receptor on the NK cell, preventing it from being destroyed.
MHC Class I Proteins: These proteins are on the surface of every nucleated cell and inhibit NK cell killing. Infected cells may down-regulate MHC class I expression, making them targets for NK cells.
Missing Self: Loss of MHC class I expression can trigger NK cell killing, marking an altered, damaged, or cancerous cell.

Complement System

Components: The complement system is a plasma protein cascade functioning in innate and adaptive immunity. It's part of an intricate network of > 50 proteins.
Alternative Pathway: A complement pathway that recognizes and destroys non-self cells (pathogens) without the need for antibodies. This pathway involves the cleavage of C3 into C3b, which forms a membrane attack complex (MAC).
Membrane Attack Complex (MAC): This complex forms a pore in the cell membrane, allowing the cell's contents to leak out, eventually destroying the pathogen cell in question.
Dissociation: Complement receptors and decay-accelerating factors help prevent the complement system from attacking healthy cells. These proteins promote the dissociation of complement convertases from host cells.
Killing Mechanisms: Complement proteins directly kill cells or mark them for phagocytosis (a process by which cells engulf and destroy pathogens).

Inflammatory Response

Purpose: Inflammation coordinates delivery of blood components for infection or injury. It controls metabolism, thermogenesis & behaviour; inflammation is essential for a proper response.
Stimuli: Inflammatory stimuli come from
outside the cell (exogenous: pathogen-associated molecular patterns [PAMPs] or chemical irritants).
inside the cell (endogenous: damage-associated molecular patterns [DAMPs] or cellular stress).
Signals: Cytokines (e.g., IL-1β, TNF-α, IL-6) are important inflammatory mediators.
Effects: The inflammatory process causes redness, swelling, heat, and pain. The purpose is to eliminate the cause of injury, contain the infection, and promote tissue repair.
Circuit: Sensors trigger signals that influence inflammatory effectors to resolve injury and activate an adaptive immune response. Negative feedback (resistance) and feed-forward (adaptation/tolerance) contribute to the circuit.

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Description

Test your knowledge on innate immunity and the complement system. This quiz covers fundamental concepts such as self-nonself discrimination, the role of natural killer cells, and the components of the complement system. Ideal for students studying immunology or related fields.