Immunology

Question 1

Which type of immunity am I describing?

- limited specificity, no memory formed, cellular components are neutrophils, NK cells and macrophages

Answer 1

Innate immunity

Question 2

What cellular components are involved in adaptive immunity?

Answer 2

B cells and T cells

Question 3

What is haematopoeisis?

Answer 3

Formation of WBC, RBC and platelets and takes place in the bone marrow

Question 4

Myeloid progenitor cells develop into myeloid cells such as?

Answer 4

Neutrophils, basophils, eosinophils, mast cells, dendritic cells, macrophages and monocytes

Question 5

Give examples of epithelial surfaces and their role in the innate immune response

Answer 5

Epithelial surfaces provide a physical barrier
Low pH of skin and fatty acid in sebum inhibit microbial growth
Gut has gastric acid, pancreatic enzymes and mucosal immunoglobulins (IgA), and normal colonic flora which stops overpopulation of microbes
Respiratory tract secretes mucus to trap organisms and cilia transport them to the throat to be coughed up or swallowed into gastric acid
Flushing of urine through urinary tract prevents microbes from adhering to the urothelium

Question 6

Give examples of phagocytes

Answer 6

Macrophages and neutrophils

Question 7

What is complement? How many pathways are there?

What is the end product?

Answer 7

Circulating proteins which assist the immune system in killing microbes
There are 3 pathways - classical (activated antibodies to a pathogen), alternative pathway (microbes lacking regulatory protein present on host cells) and the lectin pathway (mannose binding protein)
The end result is the generation of C3 converts which splits into C3 and C3b. Microbes coated in C3b are phagocytosed or killed by the membrane attack complex which punches holes in the microbe.

Question 8

What are the 4 main ways in which antibodies work?

Answer 8

1. Neutralise the biological activity of a vital microbial molecule (eg. toxin)
2. Target microbes for phagocytosis
3. Activate complement
4. Activate cytotoxic immune cells

Question 9

Which T cells are activated by Class I MHC expressed by all nucleated cells?

Answer 9

CD8+ cytotoxic T cells

Question 10

Which T cells are activated by Class II MHC expressed by all specific antigen presenting cells such as dendritic cells?

Answer 10

CD4+ T helper cells

Question 11

Where do B cells and T cells mature?

Answer 11

Both produced in thymus but T cells mature in the thymus and B cells mature in the bone marrow

Question 12

Do B cells need an antigen to be presented on MHC molecule?

Answer 12

No, they can bind to an antigen directly and then present the antigen to T cells on MHCII class receptor

Question 13

What happens when a B cell presents an antigen to a T cell?

Answer 13

The T cell gets activated, it helps the B cell mature into a Plasma Cells and memory cells. Plasma cells serve to secrete antibodies which circulate in the serum and mark pathogens for destruction by phagocytes.
Memory B cells ‘remember’ the offending pathogen to be able to mount a quicker immune response next time it is encountered.

Question 14

What happens when a T cell first encounters a pathogen?

Answer 14

The naive T cell is primed and turned into a mature T cell which causes clonal expansion of the T cells some of which are effector cells and some are memory T cells

Question 15

What are the different subtypes of T cells? What are their roles?

Answer 15

• helper Tcells (CD4)facilitate the activation of the immune response through cytokines and stimulate division and differentiation of various effector cells (B cells)
• cytotoxic T cells (CD8)– also known as killer or effector T cells. Providecell-mediated immunityby targeting and killing infected cells including cancer cells
• regulatory Tcells– also known as suppressor T cells – play a vital role in limiting the immune response to prevent excessive damage to tissues and organs
• memory T cells“remember” what has happened to allow the immune system to mount a faster, more effective response should the offending organism return

Question 16

In the immune response, which antibody (unspecific) is first produced and which (specific) antibody is produced later?

Answer 16

IgM is produced first

IgG is highly specific and is produced after

Question 17

How does the innate immune response differentiate good from bad bacteria?

Answer 17

Using pattern recognition receptors (PRRs) and pathogen associated molecular patterns (PAMPs)

Question 18

What are examples of PAMPs which the innate immune system (macrophages, neutrophils etc) can recognise on bacteria and respond to?

Answer 18

peptidoglycan, lipopolysaccharide, lipoteichoic acid, fungal wall components (mannan) and flagella proteins

Question 19

Activation of TLRs and PRRs drive what?

Answer 19

Cytokine production by APCs that increase the likelihood of successful T cell activation

Question 20

What are the main family of PRRs?

Answer 20

Toll like receptors - these play a vital role in initiation of innate immune response by detecting harmful pathogens.

Question 21

Which TLRs recognise bacterial and viral microbes

Answer 21

Bacterial: TLR 1,2,4,5,6,9,10
Viral: TLR 3,7,8

Question 22

Whats the difference between passive and active immunisation? Which provides longer term immunity?

Answer 22

Passive: provided when a person is given antibodies to a disease rather than producing them through his or her own immune system.
A newborn baby acquires passive immunity from its mother through the placenta. A person can also get passive immunity through antibody-containing blood products such as immune globulin, which may be given when immediate protection from a specific disease is needed. The major advantage to passive immunity; protection is immediate, whereas active immunity takes time (usually several weeks) to develop. Protection is not life long, it lasts a few weeks.

Active: results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Exposure to the disease organism can occur through infection with the actual disease (resulting in natural immunity), or introduction of a killed or weakened form of the disease organism through vaccination (vaccine-induced immunity). Immunity is life long but takes some time to get immunity.

Question 23

Examples of when artificial passive immunity (pooled IgG against pathogens given) might be needed?

Answer 23

• Individuals with inborn or acquired agammaglobulinaemias
• Exposure to a disease what could cause complications (immune compromised patient exposed to measles)
• When there isn’t time for active immunisation to give protection (pathogen has short incubation time)
• Acute danger of infection
• Anti-toxins and anti-venins

Question 24

does passive immunity create memory cells?

Answer 24

No

Question 25

In the primary immune response (first time seeing the pathogen) & secondary immune response (next time seeing the same pathogen) which antibodies predominate?

Answer 25

Primary: IgM which is low affinity and relies on the innate immune system
Secondary: IgG which is rapid, and does not rely on the innate immune system

Question 26

What are the 4 types of vaccines? Give an example for each

Answer 26

1. Whole cell - Live attenuated (weakened) (TB/typhoid/MMR/varicella/smallpox/rotavirus/yellow fever)
2. Whole cell Inactivated (killed, inactivated pathogen - Polio, hep A, plague, cholera, influenza, rabies)
3. Subunit - These are considered as fractionated vaccines as only 1 part of the pathogen is used to create the vaccine and includes polysaccharide vaccines (haemophilia influenza B, Hep B, HPV, bordetella pertussis, strep pneumonia, neisseria meningitidis, VZV)
4. Toxoid - Fractionated as only 1 part of the pathogen is used to create the vaccine

Question 27

Advantages and disadvantages of live attenuated vaccines?

Answer 27

Adv: activation of full natural immune response, prolonged contact with immune system, memory response, prolonged and comprehensive protection, often only 1 immunisation is needed (good for poorer countries)

Disadv: immunocompromised patients may become infected, complications such as post-infectious encephalomyelitis, occassionally the attenuated organism can revert to the virulent form and can lead to an outbreak

Question 28

Advantages and disadvantages or whole inactivated pathogen vaccines?

Answer 28

Adv: no risk of infection, storage is less critical, wide range of different antigenic components are present so a good immune response is possible.

Disadvantages: tend to just activate the humeral immune response (lack of T cell involvement), the immune system response can be quite weak, repeated boosters might be needed and patient compliance can be an issue.

Question 29

Advantages and disadvantages of subunit vaccines?

Answer 29

Adv: safe, only parts of the pathogen are used, no risk of infection, easier to store and preserve
Disadvantage: immune response less powerful, repeated vaccinations needed and adjuvants

Question 30

Which cells can present antigens really well?

Answer 30

Dendritic cells

Question 31

Most common multi lobed WBC?

Answer 31

Neutrophil

Question 32

Antigen presenting cells are presented to what?

Answer 32

T cells

Question 33

Name some vaccines administered as live vaccines

Answer 33

MMR
BCG
TB
typhoid
varicella
smallpox
rotavirus
yellow fever

Question 34

Polysaccharide vaccines are composed of long chains of sugar molecules that make up the surface capsule of certain bacteria. These vaccines are available for the treatment of which following diseases? (3)

pneumococcal disease, influenzae,
MMR,
meningococcal disease, salmonella typhi.

Answer 34

Pneumococcal disease, salmonella typhi & meningococcal disease. This attacks to polysaccharide coating on these pathogens.

Question 35

What are the 5 steps of pathogenesis?

Answer 35

1. exposure - contact
2. adhesion
3. invasion
4. infection
5. exit - transmission