Immune System Functions and Tissues Quiz

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Questions and Answers

What is the primary function of cytokines in the immune system?

They are responsible for producing antibodies.

They eliminate cell debris.

They directly kill pathogens.

They drive and orchestrate immune responses. (correct)

Which of the following organs is NOT considered a primary lymphoid organ?

Spleen (correct)

Lymph nodes (correct)

Bone marrow

Thymus

Which type of immunity is characterized by immediate response to infection?

Specific immunity

Adaptive immunity

Innate immunity (correct)

Passive immunity

What role do dendritic cells play in the immune system?

They detect pathogens and present them to lymphocytes. Signup and view all the answers

Which of the following cells is primarily involved in phagocytosis?

Macrophages Signup and view all the answers

Which cytokine is primarily associated with inducing inflammation?

Tumor necrosis factor-alpha Signup and view all the answers

What is the function of Natural Killer (NK) cells in the immune system?

They attack and destroy infected or cancerous cells. Signup and view all the answers

Which of the following is a characteristic function of adaptive immunity?

Memory response to previously encountered antigens Signup and view all the answers

What is present on all Gram-negative bacteria?

Lipopolysaccharide Signup and view all the answers

Which cells play a crucial role in phagocytosis during an immune response?

Neutrophils and macrophages Signup and view all the answers

Which process accurately describes the sequence of phagocytosis?

Recognition, Ingestion, Digestion Signup and view all the answers

What do identical Toll-like receptors recognize in different microbes?

Common structural components Signup and view all the answers

What do neutrophils and macrophages do after detecting an infection?

They can leave the blood to reach the infection site. Signup and view all the answers

Which cytokines are specifically mentioned as mediators of inflammation?

C3a, C4a, and C5a Signup and view all the answers

What is the primary function of natural killer (NK) cells?

To kill infected or cancerous cells Signup and view all the answers

What role does perforin play in the immune response?

Punches holes in cell membranes Signup and view all the answers

How do neutrophils and macrophages eliminate pathogens?

Using phagocytosis to engulf and digest pathogens Signup and view all the answers

What is the membrane attack complex primarily associated with?

Lysis of targeted cells Signup and view all the answers

What role does C3a play in the complement system?

Triggers inflammatory events Signup and view all the answers

Which pathway is activated by an antigen-antibody complex?

Classical pathway Signup and view all the answers

What is the primary function of the activated complement proteins during opsonisation?

To bind to pathogen surfaces Signup and view all the answers

Which component acts as the central element of the complement system?

C3 Signup and view all the answers

What is the result of the membrane attack complex (MAC)?

Disruption of fluid balance leading to cell lysis Signup and view all the answers

What form does the C3 convertase take in the classical pathway?

C4b2a Signup and view all the answers

Which of the following features is characteristic of innate immunity?

It recognizes non-self in a non-specific manner. Signup and view all the answers

Which component is involved in the formation of C5 convertase?

C3b Signup and view all the answers

What type of cells are primarily involved in the adaptive immune response?

B cells and T cells Signup and view all the answers

The alternative pathway primarily provides a mechanism for which aspect of the immune response?

Immediate pathogen recognition Signup and view all the answers

Which statement about the adaptive immune system is true?

It recognizes antigens with high specificity. Signup and view all the answers

Which are included in the cells of the innate immune system?

Natural Killer Cells Signup and view all the answers

What role do Pathogen Recognition Receptors (PRRs) play in the innate immune response?

They bind to pathogen-associated molecular patterns (PAMPs). Signup and view all the answers

Which of the following statements correctly describes the innate immune response compared to the adaptive immune response?

It is always functional from birth. Signup and view all the answers

Which cell type is NOT part of the adaptive immune system?

Dendritic cells Signup and view all the answers

What distinguishes the adaptive immune system's memory function?

It can only recognize pathogens after the first exposure. Signup and view all the answers

Study Notes

Functions of the Immune System

The immune system protects the body from pathogens and disease
It fights cancer
It promotes wound healing and tissue regeneration
It removes cellular debris

Tissues of the Immune System

Primary Lymphoid Organs : Where immune cells are formed and mature
- Bone Marrow
- Thymus
Secondary/Peripheral Lymphoid Organs: Where immune cells are concentrated and function
- Lymph Nodes
- Spleen
- Mucosal Immune System

Cells of the Immune System

Circulating Cells: Travel between the blood and tissues:
- Neutrophils, Monocytes/Macrophages, Eosinophils, Lymphocytes
Resident Cells: Remain in tissues:
- Dendritic cells, Macrophages, Mast cells

Cytokines: Important Effectors of Immune Function

They are small proteins (5-20kDa)
They are secreted by cells and can act on the cell that produced it (autocrine) and nearby cells (paracrine)
They bind to specific receptors on cells
Key types: Interleukins (IL-1-IL-22); Interferons (IFN-α, β, γ); tumour necrosis factors (TNF- α, β), transforming growth factor-β (TGF-β)
Each immune cell secretes a characteristic profile of cytokines that determine the function of that cell
They drive and orchestrate immune responses

The Two Main Branches of the Immune System

Innate Immunity:
- Physical barriers (skin, lysozyme in secretions)
- Phagocytosis
- NK cells
- Complement
- Inflammatory mediators and antimicrobial peptides released from innate cells
Adaptive Immunity:
- Antibodies: B cells (B lymphocytes)
- Cell-mediated Immunity: T cells (T lymphocytes)

Cells of the Innate and Adaptive Branches

Innate: Monocytes/Macrophages, Neutrophils, Eosinophils, Basophils, Mast Cells, Dendritic Cells, Natural Killer Cells
Adaptive: Lymphocytes, B cells, T cells

Features of Innate/Natural Immunity

Present at birth
Always active
Responds immediately
Instructs the adaptive immune system
Recognizes non-self in a non-specific way
No memory function

Features of Adaptive/Acquired Immunity

Develops over a lifetime
Slower response time than innate
Recognizes antigens with high specificity
Has a memory function

Innate Immune System

Pathogen Recognition by Cells of the Innate System

Non-specific recognition
Innate cells express Pathogen Recognition Receptors (PRRs)
- Toll-like receptors
They bind to pathogen-associated molecular patterns (PAMPs)
- Structures on microbes
- Shared by groups of microbes

Innate Immune Recognition of Bacterial Cell Wall Components

Gram-negative bacteria: TLRs recognize lipopolysaccharides (LPS)

Innate Functions: Phagocytosis & Destruction of Pathogens

Neutrophils and macrophages are key phagocytes
They leave the blood and travel to sites of infection
Phagocytosis involves recognition, ingestion, and digestion

Complement

30 plasma proteins that circulate in an inactive state
They become activated at sites of infection and trigger inflammatory events
C3 is the central component
** Pathways:**
- Classical pathway (activated by antigen-antibody complexes)
- Alternative pathway
- Lectin pathway
** Functions:**
- Inflammation (C3a, C4a, C5a)
- Opsonisation (C3b, C4b bind to pathogen surface and increase phagocytosis)
- Cell lysis (Membrane Attack Complex, MAC)

Natural Killer Cells

Lymphocytes (10-15% of blood lymphocytes)
Recognize cells infected with viruses or become cancerous
These cells have lost or modified surface structures
They kill infected cells through the release of:
- Perforin: Punches holes in the cell membrane
- Granzyme: Enters cells via perforin pores and induces apoptosis (cell death)

Summary of Main Points

The immune system is made up of cells and tissues that protect the body
Cytokines are small proteins crucial for immune cell communication and response
The innate and adaptive immune systems differ in their speed of response and specificity
Phagocytosis is a key function of innate immunity, carried out by neutrophils and macrophages
Complement system contributes to opsonisation, inflammation, and cell lysis.
Natural Killer Cells use perforin and granzyme to target pathogens

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Description

Test your knowledge on the immune system's functions, tissues, and cellular components. This quiz will cover the different types of lymphoid organs, immune cells, and the role of cytokines in immune response. Perfect for students studying immunology.