Principles of Innate Immunity

Questions and Answers

What is the primary role of phagocytosis in the immune response?

It prevents inflammation by removing DAMPs.

It allows for the antigen presentation of external pathogens. (correct)

It induces necroptosis in infected cells.

It clears apoptotic cells from the tissue.

How do apoptotic cells contribute to inflammation?

By inducing phagocytosis directly.

By releasing DAMPs into the surrounding environment.

By sequestering DAMPs in apoptotic bodies. (correct)

By enhancing the activity of killer T cells.

What distinguishes necroptosis from apoptosis in terms of DAMPs?

Apoptosis releases more DAMPs than necroptosis.

Both necroptosis and apoptosis sequester DAMPs in the same way.

Necroptosis releases DAMPs, while apoptosis sequesters them. (correct)

Necroptosis does not involve DAMPs at all.

What is a significant function of programmed cell death in the context of infection?

It helps eliminate the replicative niche for pathogens. Signup and view all the answers

Which factor significantly affects the immunogenic activity of programmed cell death (PCD)?

The sequestration versus release of DAMPs. Signup and view all the answers

What is the primary role of lysozyme in innate immunity?

To degrade bacterial cell walls Signup and view all the answers

Which statement accurately describes the C3 convertase in complement pathways?

It forms the foundation for the C5 convertase Signup and view all the answers

What initiates the classical complement pathway?

C1q binding to antibodies Signup and view all the answers

How do defensins contribute to innate immunity?

By disturbing microbial membrane integrity Signup and view all the answers

What is the role of C3b in the immune response?

To serve as an opsonin Signup and view all the answers

What phenomenon results from anaphylatoxin signaling?

Promotion of inflammation Signup and view all the answers

Which pathway of complement fixation is triggered by carbohydrates on pathogen surfaces?

Lectin pathway Signup and view all the answers

The formation of the membrane attack complex (MAC) involves which of the following components?

C5b, C6, C7, C8, and C9 Signup and view all the answers

Which type of receptors do phagocytes use to recognize pathogens?

Phagocytic receptors for PAMPs and opsonins Signup and view all the answers

Which complement pathway begins spontaneously?

Alternative pathway Signup and view all the answers

Study Notes

Principles of Innate Immunity

Innate immunity consists of physical and chemical barriers that prevent infections.
Lysozyme is effective at degrading bacterial cell walls.
Defensins disrupt the integrity of microbial membranes.
Antibodies create a link between adaptive and innate immunity.
Multiple layers of immune defense include barriers, innate immune cells, and adaptive immune cells, each with distinct functions.

Barrier Tissues and Antimicrobial Agents

Barrier tissues protect against microbial colonization through mechanical and chemical defenses.
Native flora compete with and inhibit pathogenic flora.
Antimicrobial agents, like lysozyme and defensins, provide broad-spectrum protection against infections.

Complement System Overview

The complement system includes pathways that converge on the cleavage of C3, initiating various immune responses like inflammation, phagocytosis, and membrane attack.
The classical pathway commences with C1, where C1q binds to antibodies, leading to enzymatic activation.

Complement Pathways

The classical pathway is primarily triggered by antibodies, while the lectin pathway is activated by carbohydrates on pathogen surfaces, and the alternative pathway can initiate spontaneously.
All pathways generate a C3 convertase, critical for further antimicrobial activity.

Effector Functions of the Complement System

C3 cleavage activates inflammation, opsonization, and the formation of the membrane attack complex (MAC).
C3b acts as an opsonin, marking pathogens for phagocytosis and facilitating the clearance of immune complexes.
C5 convertase formation leads to MAC assembly, ultimately resulting in the lysis of target cells.

Phagocytosis and Programmed Cell Death

Phagocytic receptors identify pathogen-associated molecular patterns (PAMPs) and opsonins, enabling efficient pathogen recognition and engulfment.
Phagocytosis helps present antigens from external pathogens and clears dead cell debris.
Apoptosis, which can be triggered by infection, sequesters DAMPs (damage-associated molecular patterns) and can enhance inflammatory responses.
Necroptosis, a programmed form of necrosis, releases DAMPs and is also immunogenic.

Key Outcomes and Immune Responses

Phagocytosis connects innate and adaptive immune responses through antigen presentation.
Phagocytes utilize harsh environments within phagolysosomes and cytoplasmic granules for antimicrobial actions.
Programmed cell death limits pathogen replication and modulates immune responses. The immunogenicity of DAMPs can influence inflammation, depending on their release or sequestration.

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Description

This quiz covers the fundamental concepts of innate immunity, including the physical and chemical barriers that protect organisms from infection. It also discusses the role of lysozyme, defensins, and the interaction between innate and adaptive immune systems. Test your understanding of how these defenses work together to provide broad protection.