Introduction to Immunology

Question 1

What are histocompatibility genes ? What is their major downside ?

Answer 1

Give us slightly different immune responses. Do not allows for easy organ/tissue transplant.

Question 2

How do HIV infections work ?

Answer 2

Damage some types of immune cells and their ability to recognise and respond to certain pathogens.

Question 3

Which of these are extracellular and which are intracelullar ?
Influenza, malaria, tuberculosis, streptococcus

Answer 3

Influenza: replicates inside the cell where new viruses are released (INTRA)
Malaria: Go through both extra and intracellular phases (BOTH)
Tuberculosis: Spend most time hidden in macrophage but can survive outside (MOSTLY INTRA)
Streptococcus: Partly in and partly out

Question 4

What are the kinds of defence mechanisms we have ?

Answer 4

Innate and Adaptive

Question 5

What are the main features of the innate immune system ?

Answer 5

• First line of defence
• Does not improve with exposure
• Series of pre-formed effector molecules circulating in body

Question 6

What are the main features of the adaptive immune system ?

Answer 6

• 2nd line of defence
• Improved by further exposure (faster and stronger response)
• Can take some time to get going
• Specific (can make response against specific part of pathogen and keep memory of it)

Question 7

What are examples of barriers to infection ?

Answer 7

Physical barriers (skin, epithelia, movement of cilia, trapping by mucus) 
Biochemical barriers (low pH in sweat, vaginal and stomach excretions, lysozymes in secretions)

Question 8

What does the body respond if the barriers to infections are breached ?

Answer 8

1. Attempt to contain and localize

2. Phagocytic cells

Question 9

What are the two main types of cells in the monocyte/macrophage lineage ?

Answer 9

Monocytes moving to site of infection and maturing into macrophages once they get to the tissue
Fixed tissue macrophages

Question 10

What are the main steps in the process of phagocytosis ?

Answer 10

1. Engulfing
2. Lysosome fusion (contains toxic agents)
3. Release of microbial product

Question 11

What are acute phase proteins ?

Give an example.

Answer 11

Proteins whose “concentrations increase (positive acute-phase proteins) or decrease (negative acute-phase proteins) in response to inflammation”.
C-reactive protein. Made by liver cells and circulates around but shoots up within few hours of infection. Its function is to act as an opsonin and to bind to lipids on dead cells and help them get cleared away.

Question 12

What are complement proteins ?

Give an example.

Answer 12

Proteins which “enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen’s plasma membrane” when the complement cascade is triggered. They may do that through:

1- Trigger complement pathway C1 to C9 (C9 can lyse certain species of bacteria by forming holes on bacterial surface and hence contents leak out)
2- Certain fragments of of complements are chemotactic agents (C5a and C3a)
3-Other parts of the complement cascade are opsonins

There are complement from C9 down to C1.

Question 13

What protein groups are important in the immune response ?

Answer 13

Complement Proteins
Acute phase Proteins
Interferons
Cytokines

Question 14

What are interferons ?

Give examples.

Answer 14

-Three kinds: 
IFN alpha (widespread release by range of cells but mostly leukocytes)
IFN beta (widespread release by range of cells but mostly fibroblasts)
IFN gamma (much more restricted to be released by cells of the immune system, esp. T lymphocytes).

-Function:
Virus infected cells have a detection mechanism telling them they have a virus inside. They then release IFN alpha and beta which will allows nearby cells to put in place mechanisms (such as turning off system allowing virus to replicate or changing itself to make itself resistance to infection) to prevent them from getting infected themselves (but does not save infected cell itself).
Interferon gamma is released by some types of lymphocytes T after activation by antigen, since they (IFN gamma) are strong activators of immune reponses.

Question 15

What are cytotoxic T cells and how do they work ? (=CD8+ killer cell)

Answer 15

Part of adaptive immune system response.
Virus-infected cells have protein fragments from virus on their surface. Cytotoxic T cells detect these fragments and are able to kill virus infected cells and eliminate virus by means of antibodies.

Question 16

What happens if virus infected cells use immunoinvasion strategies such as changing their surface?

Answer 16

Cytotoxic T cells can’t do anything (evades them) BUT natural killer cells detect cells altered by viruses.

Question 17

What are the functions of antibodies ?

Answer 17

• Recognise antigens (most of the time just 1) and binds pathogens on their binding site
• Their back end bind onto phagocytic cells
• Their back end can triggering complement cascade
• Binding to virus receptor to block infection of cell

Question 18

Which factors optimise the binding of binding of phagocyte onto pathogen ?

Answer 18

Opsonisation (by complement system component) and antibody (binding the pathogen and phagocyte at the same time)

Question 19

Which antibodies are notably made and why does the adaptive immune response take time ?

Answer 19

• when first injecting antigen, first make IgM and IgG response comes later (primary response)
• If same antigen comes again, same amount of IgM but faster and larger amount of IgG (secondary response)

That is how vaccines work (booster aimed in case weak immune primary response)

Question 20

What are plasma cells (AKA plasma beta cells) ?

Answer 20

Cells which produce antibodies.

Question 21

What is autoimmune haemolytic anaemia ?

Answer 21

Antibody are produced by the plasma cells, trigger the complement cascade and cause the lysis of RBSs

Question 22

How does the immune system work in a foetus ?

Answer 22

• Transfer of maternal IgG main defence for first few months before and after birth (some immunoglobins can cross the placenta during pregnancy)
• This is aided by the fact that during pregnancy, oestrogen stimulates IgG and IgA production
• Oestrogen also inhibits T cells which could reject the foetus (in rare cases, autoimmune response against male antigens in foetus but in 1/3 cases most autoimmune conditions get better with pregnancy).

Question 23

What happens when the immune system goes wrong ?

Answer 23

May result in:

• Hypersensitivity (against innocuous antigens)
• Auto-immunity (against self-antigen + loss of tolerance)
• Immunodeficiency as a result of infection

Question 24

What are 2 kinds of autoimmune responses ?

Answer 24

• Cell-mediated response

- Generation of antibodies (e.g. severe anaemia)

Question 25

Give examples of autoimmune diseases. What are their main features ?

Answer 25

• Rheumatoid Arthritis- Damage to synovial membrane and bone in many joints. Treated through pain relief + steroid and antibodies interfering with immune response
• Type 1 Diabetes Mellitus(/IDDM)- Cytotoxic T cells kill beta secreting cells of pancreas (insulin storing and secreting cells)
• Thyroiditis- Inflammation to thyroid gland. In Hashimoto’s thyroiditis, enlarged thyroid.
• Against hormones: Antibody binds onto hormone which is then cleared away from system (hormone deficient) OR antibody binds onto surface receptor which is then internalised (so hormone can no longer bind onto it) OR antibody activates receptor in absence of hormone (overstimulation).

Question 26

What are the antibodies involved in attacking the body’s own proteins called ?

Answer 26

Autoantibodies