An Introduction to immunology (physiology)

Question 1

A protein molecule that binds with high affinity to specific antigens:

Answer 1

Antibody

Question 2

A substance that can bind to an antibody or T-cell receptor. Can be self or non-self:

Answer 2

Antigen

Question 3

The specific surface feature of an antigen that binds to the antibody:

Answer 3

Epitope

Question 4

The process by which cells “expose” or “present” an antigen to other cells of the immune system:

Answer 4

Antigen presentation

Question 5

Small signalling proteins that regulate the activity of the immune system, by interacting with specific cytokine receptors on target cells:

Answer 5

Cytokines

Question 6

A substance that binds to a pathogen making it more susceptible to phagocytosis:

Answer 6

Opsonin

Question 7

A cell type that can internalise substances and microorganisms to inactive/kill them:

Answer 7

Phagocyte

Question 8

A type of immune cell that contains granules within the cytoplasm. These granules are filled with protein-based signalling molecules, and can be released in response to specific signals:

Answer 8

Granulocyte

Question 9

Nomenclature system used for the purposes of immunophenotyping cells:

Answer 9

Cluster of differentiation

Question 10

A protein complex that presents an antigen to other cells of the immune system:

Answer 10

Major histocompatibility complex (MHC)

Question 11

What are the three arms of the immune system? (6)

Answer 11

•Physical barriers
-Chemical, mechanical and biological barriers.
• Innate immune system
-Pattern recognition receptors, phagocytes, NK cells…
•Adaptive immune system
-T-cells, B-cells and antibodies
Note:Specificity increases as you go down.

Question 12

What are some of the examples of the physical barriers of the immune system?

Answer 12

Mechanical-Skin, flushing.
Chemical-Peptides, acids and enzymes.
Biological-Commensal flora in various body compartments.

Question 13

What are active phase proteins?

Answer 13

Proteins secreted by the liver in response to cytokines (IL-1, IL-6 and TNFa) released by pro-inflammatory immune cells.

Question 14

What are the three acute phase proteins and which role do they each play? (6)

Answer 14

-Serum amyloid A: Recruit immune cells to inflammatory sites and induce enzyme that degrade the extracellular matrix.
-Lactoferrin- Bind to iron in order to reduce free iron to pathogens and tumour cells.
-C reactive proteins- activate complement, induces apoptosis and phagocytosis.

Question 15

Which two types of antigens are recognised by the pattern recognition receptors in the innate immune system? (2)

Answer 15

Pathogen associated molecular patterns (PAMPs) and Damage associated molecular patterns (DAMPs)

Question 16

Which receptors recognises PAMPs?

Answer 16

Toll-like receptors (TLR)

Question 17

What role does the ff cells play in phagocytosis:
1. Neutrophils
2. Macrophages
3. Dendritic cells
4. Epithelial cells

Answer 17

1. Eliminate invading microorganisms by intracellular killing.
2. Eliminate exogenous pathogens, host-derived molecules and dead cells.
3. Induces the adaptive system by presenting antigens to T-cells.
4. Eliminates neighbouring dead cells.

Question 18

What is the role of basophils?

Answer 18

It is involved in the host defence against parasitic worms.

Question 19

What are the functions of eosinophils? (3)

Answer 19

-Releases proinflammatory mediators in response to various immunoglobulins and cytokines.
-Involved in allergic response.
-Secretes major basic protein (MBP) which increases the permeability of the membrane and can kill parasites.

Question 20

One role of NK cells?

Answer 20

Secretes enzymes that bore holes in cell membranes of infected cells.

Question 21

Functions of cytokines? (5)

Answer 21

•Play important role with regards to:
-Inflammation
-Anti-virus activity
-Interleukins
-Inhibition/activation of the immune system
-Chemotaxis

Question 22

What are the three pathways of complement?

Answer 22

Classic pathway: predominantly results in the formation of the membrane attack complex.
Alternative pathway: results in increased phagocytosis.
Lectin pathway: Regulates inflammation by attracting macrophages and neutrophils.

Question 23

Explain the role of the C3 convertase enzyme in complement and how the MAC is activated (5)

Answer 23

-The C3 convertase enzyme is produced through alternative mechanisms by the 3 pathways.
-The C3 convertase enzyme cleaves the C3 protein into C3a and C3b.
-C3b is responsible for opsonisation and phagocytosis of pathogens.
-Through a series of biochemical reactions, the C3b is converted into C5 convertase enzyme. This occurs in both the classic and alternative pathways.
-The C5 convertase is responsible for the activation of the Membrane Attack Complex which kills pathogens.

Question 24

What are the end products for the three complement pathways? (3)

Answer 24

-The alternative pathway results in increased opsonization which leads to increased phagocytosis.
-The classic pathway results in the formation of the membrane attack complex (MAC) which is resp for bacterial lysis.
-The lectin pathway results in the degranulation of mast cells which triggers histamine release.

Question 25

Explain the maturation process of T-cells (5)

Answer 25

•Maturation occurs in the thymus.
•Thymus releases chemokines which attract the T-cells towards it and promotes the formation of CD4 and CD8 receptors and T-cell receptors.
•These receptors are supposed to bind to the thymic epithelial cells, if they are recognised as foreign they die (apoptosis).
•The remaining cells are now exposed to self cells, if they bind to them they are killed, because we don’t want the T-cells that can kill our own cells.
•They then enter the cortex of the thymus and mature there.

Question 26

What are the characteristics of the TH1 response? (6)

Answer 26

-IL-2, IFNgamma
-proinflammatory
-Increased phagocytic activity
-Releases vasodilatory compunds
- killing of intracellular pathogens
-may lead to tissue damage

Question 27

What do we call the immunosuppressing T-cells?

Answer 27

T regulatory cells (Tregs)

Question 28

What are the functions of antibodies? (5)

Answer 28

P recipitation: It causes soluble antigen to insoluble, aiding elimination.
A gglutination: Links cell bound antigens, causing agglutination.
N eutralisation: Masks dangerous parts of pathogens.
I nflammation: Triggers histamine release, which causes inflammation.
C omplement: Leads to production of complement proteins which are responsible for cell lysis.

Question 29

What mediates the immediate hypersensitivity reaction in allergic reactions?

Answer 29

Antibodies

Question 30

What mediates the delayed hypersensitivity reaction in allergic reactions? (2)

Answer 30

Helper T-cells and macrophages