Immunology

Question 1

Explain the terms:

a) Clinical infection
b) Sub-clinical infection
c) Lactrogenic (nosomical) infection

Answer 1

a) Clinical = Infections with signs and symptoms
b) Sub-clinical = Infections with pathogens, however no
symptoms
c) Lactrogenic = Infections from a medical practitioner
or due to interventions.

Question 2

How are respiratory infections transmitted?

Answer 2

• Droplets (sneeze/cough)
• Saliva
• Dust and soil
• Water aerosols

Question 3

Zoonoses is a term used for what type of disease?

Answer 3

Zoonoses are infectious diseases that can be naturally transmitted between animals (usually vertebrates) and humans. They can be transmitted via:

• Direct animal-human contact
• Animal-vector-human
• Human-vector-animal

Question 4

Explain the terms:

a) endemic
b) epidemic
c) pandemic
d) sporadic

Answer 4

a) Endemic - a disease that is present in a community
(region) all of the time; usually only clinical in a few.
b) Epidemic - widespread disease within a community
(region); affects many people but not only
occasionally present.
c) Pandemic - widespread epidemic; not confined to a
single community or region; present in more than
one continent.
d) Sporadic - widely scattered disease that occurs singularly, irregularly and non-frequently.

Question 5

What is epidemiology?

Answer 5

Epidemiology is the study of the determinants and distribution of disease; how it occurs in different populations and why.

Question 6

Explain the difference between mortality and morbidity.

Answer 6

Mortality refers to the number of deaths caused by an ineffective agent, where as morbidity refers to the number of illnesses caused by the agent.

Question 7

In epidemiological terms, how would you classify AIDS?

Answer 7

AIDS is a widely distributed disease worldwide and so would be classified as a pandemic.

Question 8

What factors influence the spread of a disease?

Answer 8

• The pathogens virulence.
• The transmission of the pathogen.
• The susceptibility of the population; their immunity.

Question 9

List four ways of preventing the spread of disease in a community.

Answer 9

• Immunisations.
• Education.
• Prevent contamination of water supplies.
• Proper sewage treatment and disposal.

Question 10

Which disease out of gastroenteritis, STI and a respiratory disease would spread quickly through Perth and why?

Answer 10

A respiratory disease, as Perth’s population tend to have higher hygiene standards and good public education, making gastroenteritis and and STI less likely to spread quickly. A respiratory disease may be spread via droplets, and so when people cough or sneeze without covering, infectious pathogens can be transmitted.

Question 11

List the stages of infectious disease.

Answer 11

• Incubation
• Prodromal
• Invasive phase
• Decline phase
• Convalescene phase

Question 12

What are the two branches of the immune system?

Answer 12

The immune system can be divided into two parts; innate and adaptive immunity. Innate immunity refers to non-specific defence mechanisms that come into play immediately, or within hours, of an unknown antigens detection. It is a generic response, and therefore does not require previous exposure to the antigen. Adaptive immunity on the other hand, is antigen specific. This involves the recognition of the foreign invader followed by an antibody mediated response (humoral), or cell-mediated response, in which B-cells and T-cells produce antibodies or cells to fight the antigen and produce memory cells for if a second exposure where to occur.

Question 13

What WBC’s phagacytose?

Answer 13

• Neutrophils
• Eosinophils
• Monocytes

Question 14

What WBC’s are granulated and non-granulated?

Answer 14

GRANULATED:

• Basophil
• Eosinophil
• Neutrophil

NON-GRANULATED:

• Lymphocyte
• Monocyte

Question 15

What type of WBC is mainly involved in the adaptive immune system?

Answer 15

Lymphocytes:

• B-cells
• T-cells
• NK cells

Question 16

What antibody types are involved in the primary and secondary immune response?

Answer 16

• Primary = IgM (immunoglobin M)

- Secondary = IgG (immunoglobin G)

Question 17

What type of lymphocyte is involved in cell-mediated immunity?

Answer 17

• T-cells

- NK cells

Question 18

List the ways that antibodies fight infection.

Answer 18

• Activate complement; punches wholes in bacteria.
• Trigger phagocytosis (opsinisation).
• Neutralise viruses and toxins (so that they cannot
  enter cells).
• Agglutination.

Question 19

List the antibody isotypes.

Answer 19

IgG
- monomer, most abundant in serum.
- largest amount, long term immunity, can cross
placenta.

IgA
- monomer in serum, dimer in saliva and secretions,
most abundant total.
- saliva and mucosal surfaces, tear, nasal fluids, milk.

IgM

• pentamer, primary response.
• first antibody to appear during an infection.

IgE
- monomer, stem binds mast cells, basophils and
eosinophils causing release of granules.
- anti-parasite, allergy

IgD
- monomer, attached to B cells, antigen receptor for
activation.
- largest antibody - Ag receptor on B cells.

Question 20

How does the skin protect against bacteria?

Answer 20

The skin is the largest organ in the body and is a part of the body’s first line of defence. It is a waterproof mechanical barrier which separates the environment from the inside of the body, allowing no bacterial agents to enter, unless it has been broken. On the skins surface grows beneficial bacteria (NF), which also aids in fighting off foreign pathogens, preventing them from entering the body.

Question 21

What are the four cardinal signs of inflammation and how do they become about?

Answer 21

• Heat - increased blood flow to the area.
• Redness - increased blood flow to the area.
• Swelling - capillaries become ‘leaky’ and fluid
  accumulates.
• Pain - pain receptors being pressured and he build up
  of toxins.

Question 22

Describe the difference between humoral immunity and cell-mediated immunity.

Answer 22

Both humoral and cell-mediated immunity form a part of the adaptive immune system; generating an antigen-specific response at the onset of infection. The main difference between the two is that in humoral immunity, B-cells are activated to produce antibody producing plasma cells, and in cell-mediated immunity T-cells destroy the antigen by inducing apotosis (programmed death cells). Both branches of the adaptive immune system produce memory cells, which aid to increase the rate of response if a subsequent infection were to occur.

Question 23

List and describe the types of T-cells.

Answer 23

Cytotoxic T-cells - these cells display MHC class 1 associated Ag via T-cell receptor + CD8. They destroy host cells that harbour anything foreign, and are responsible for cell-mediated immunity.

T-helper cells - these cells stimulate and modulate the activities of other immune cells. They detect MHC2 presented Ag via T-cell receptor + CD4. Activate macrophages, T-cells and B-cells. TH1 generally T-cells, stimulate inflammation and activate macrophages. TH2 generally help B-cells by direct contact and promote eosinophils.

T-regulator cells - these cells suppress the immune response by direct contact or inhibitory cytokines.

Question 24

What is MHC and what is its purpose?

Answer 24

MHC refers to the Major Histocompatabilty Complex. The function of MHC is to bind peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T-cells. The consequences are almost always deleterious to the pathogen; viruses infected cells are killed, macrophages are activated to kill bacteria living in their intracellular vesicles, and B-cells are activated to produce antibodies that eliminate or neutralise extracellular pathogens.

Question 25

Describe the difference between passive and active immunity.

Answer 25

• Passive immunity relies on the administration of
  antibodies (already directed against an antigen),
  whereas active immunity involves the administration
  of the antigen.
• Passive immunisations are generally administered
  post infection/toxin, wheres active immunisations are
  prophylaxis, to prevent future infection.
• In passive immunity, the recipient does not produce
  an immune response of their own, unlike in active
  immunity where they produce their own antibodies
  and memory cells.
• Passive immunity is short lived, whereas active
  immunity is long term.

Question 26

How do autoimmune diseases occur?

Answer 26

Autoimmune diseases occur when, instead of attacking foreign bacteria, viruses, or other sources of infection, the immune system attacks healthy organs and tissues. It’s not known why this happens, although conditions most often affect people with a genetic predisposition. Type 1 diabetes is an example.