Biochemistry II: Immunity

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Questions and Answers

What is the first step involved in phagocytosis?

The cell ingests the particle, and the particle is enclosed in a vesicle.

A lysosome fuses with the phagosome and the particle is digested.

The cell that will perform phagocytosis is activated. (correct)

The cell attaches to the particle that it will ingest.

Which of the following immune cells is involved in antigen presentation?

Dendritic cells (correct)

Macrophages

B cells

Mast cells

What is the role of the membrane attack complex (MAC) in complement activation?

To produce antibodies against bacteria

To activate the immune cells

To stimulate macrophages to release cytokines

To kill Gram-negative bacteria through osmotic lysis (correct)

Which cytokines are elevated in bacterial septic shock?

Tumour necrotic factor-alpha (TNF-α) and Interleukin-1 (IL-1) Signup and view all the answers

What is the function of C5 convertase in complement activation?

To cleave C5 into C5a and C5b Signup and view all the answers

Which immune cell is involved in the allergic response?

Mast cells Signup and view all the answers

What is the result of the influx of Ca2+ through the membrane attack complex (MAC)?

Osmotic lysis of Gram-negative bacteria Signup and view all the answers

What is the function of complement protein C6 in the assembly of the membrane attack complex (MAC)?

To bind to C5b Signup and view all the answers

What is the primary characteristic of innate immunity?

It is generic or non-specific in nature Signup and view all the answers

Which of the following immune cells are involved in acquired immunity?

B cells and T cells Signup and view all the answers

What is the immediate response of innate immunity to an invading microorganism?

It is activated immediately Signup and view all the answers

During an inflammatory response, what is the primary function of chemotaxis?

To facilitate the migration of leukocytes to the site of insult Signup and view all the answers

What is the main difference between innate and acquired immunity?

Innate immunity is immediate, while acquired immunity takes time to develop Signup and view all the answers

Which of the following is a characteristic of acquired immunity?

It is adapted to defend against specific pathogens Signup and view all the answers

During an inflammatory response, what is the primary function of vascular changes?

To increase blood flow to the affected area Signup and view all the answers

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

To phagocytose and eliminate pathogens Signup and view all the answers

What is the primary function of the hydrophobic site exposed on C7 in the complement system?

To anchor the complex into the pathogen's lipid bilayer Signup and view all the answers

How do tumour antigens inhibit the immune system?

By accumulating specific metabolites and signal factors within the TME or limiting the nutrients available to immune cells Signup and view all the answers

What is the primary component of the MAC?

Polymerized complement C9 Signup and view all the answers

What is the effect of high acidity and lactate on T cells?

Inhibited glycolysis and metabolism Signup and view all the answers

What type of structures are blood group antigens synthesized on?

Type 1, 2, 3, or 4 structures Signup and view all the answers

What is the difference between type 3 and 4 structures?

The R group attached to the Galβ1-3GalNAc-R structure Signup and view all the answers

What is the function of C8αγ in the complement system?

To anchor the complex into the pathogen's lipid bilayer and initiate polymerization of C9 Signup and view all the answers

What is the effect of tumour antigen-induced T cell exhaustion?

Inhibited T cell metabolism and glycolysis Signup and view all the answers

Study Notes

Innate Immunity vs Acquired Immunity

Innate immunity is inborn and activated immediately in response to an invading microorganism
Acquired immunity is adapted by the body to defend against an invading pathogen
Innate immunity is generic or non-specific in nature, while acquired immunity is specific
Innate immunity is present from birth, while acquired immunity develops over time
Aspects of innate immunity, such as mechanical barriers, exert defensive mechanisms regardless of the presence or absence of an invading pathogen
Innate immunity is triggered immediately in response to infection, while acquired immunity takes time to develop and exert its effects
Major immune cells involved in innate immunity include NK cells, neutrophils, macrophages, eosinophils, and basophils
Major immune cells involved in acquired immunity are primarily lymphocytes, including B cells and T cells

Inflammatory Response

Three major immunological events occur during an inflammatory response:
- Vascular changes: increased blood flow and fluid and plasma protein leakage into the inflamed tissue
- Cellular infiltration: leukocytes adhere to vascular endothelium and migrate through the endothelial layer to access surrounding tissues
- Chemotaxis: leukocytes follow a chemical gradient to the site of insult and unleash potent killing mechanisms

Phagocytosis

Five processes involved in phagocytosis:
- Activation of the cell that will perform phagocytosis
- Chemotaxis occurs in the immune system
- The cell attaches to the particle that it will ingest
- The cell ingests the particle, which is enclosed in a vesicle (phagosome)
- A lysosome fuses with the phagosome, and the particle is digested

Immune Cells

Examples of immune cells involved in different responses:
- Allergic response: Mast cells
- Phagocytosis: Macrophages
- Production of antibodies: B cells
- Antigen presentation: Dendritic cells

Complement Activation

Complement activation leads to the formation of the membrane attack complex (MAC), which kills Gram-negative bacteria
The MAC is formed through the assembly of C5b, C6, C7, C8, and C9 proteins
The MAC causes osmotic lysis of bacteria through the influx of Ca2+ and other electrolytes

Cytokines in Bacteria Septic Shock

Tumour necrotic factor-alpha (TNF-α) and Interleukin-1 (IL-1) are elevated in bacteria septic shock
Gram-negative bacteria, such as E. coli, K. pneumoniae, P. aeruginosa, and E. aerogenes, have cell wall endotoxins that stimulate macrophages to release TNF-α and IL-1

Membrane Attack Complex (MAC) Formation

Assembly of the MAC is initiated when the complement protease C5 convertase cleaves C5 into C5a and C5b
The MAC is formed through the binding of C5b, C6, C7, C8, and C9 proteins, leading to the formation of a transmembrane pore

Tumour Antigens

Two mechanisms employed by tumour antigens to evade immune responses:
- Inhibiting the immune system: Tumours inhibit or evade the immune system by accumulating specific metabolites and signal factors, or limiting the nutrients available to immune cells
- Inducing T cell exhaustion: Cancer cells affect the metabolism of T cells, inhibiting glycolysis and affecting the immune response

Blood Group Antigens

Blood group antigens are found on N-glycoproteins, O-glycoproteins, and glycolipids on RBCs and other cells
They are synthesized on type 1, 2, 3, or 4 structures
Type 1 and 2 structures are Galβ1-3GlcNAc-R and Galβ1-4GlcNAc-R, respectively
Type 3 and 4 structures are Galβ1-3GalNAc-R, with differing R groups

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Description

Test your understanding of immune responses in this Biochemistry II quiz. Covers the differences between innate and acquired immunity.