Topic 12: Immune System & Disease Resistance

Question 1

What is involved in innate immune defenses?

Answer 1

• Physical barriers (skin, mucous, etc)
• Mechanical barriers (tears, sweat, cilia, coughing, etc.)
• Chemical barriers
• Normal flora (outcompete newcomers)
• Phagocytes (macrophages & neutrophils)
• Inflammation (local tissue damage ⇒ release of chemicals)
• Fever
• Natural killer cells (type of lymphocyte)

Question 2

What are 2 examples of chemical barriers?

Answer 2

Gastric acid, lysozyme (in saliva/tears)

Interferons: produced by virus infected cells: trigger mechanisms in nearby uninfected cells

Question 3

Inflammation releases chemicals due to local tissue damage. What is an example of one of these chemicals?

Answer 3

Histamine (vasodilator) from mast cells (found in CT)

Result: vasodilation (⇒ swelling), heat, redness, pain = loss of function
~> attracts neutrophils, then macrophages

Question 4

What occurs during a fever?

Answer 4

Immune cells and microbe chemicals trigger release of prostaglandins in
hypothalamus ⇒ ⇑ temp

Question 5

Which medications reduce fever?

Answer 5

-aspirin
-ibuprofen
-acetaminophen

⇓ prostaglandin synthesis

Question 6

What are adaptive defenses?

Answer 6

Production of specific lymphocyte or antibody against recognized antigen

Question 7

What is the difference between antigens and antibodies?

Answer 7

Antigen (Ag): protein/polysaccharide ~>recognized as foreign by immune system
e.g. parts of bacteria, viruses, pollen, parasites, transplants

Antibody (Ab): plasma protein (γ globulin) ~> matches a specific Ag - produced by plasma cells

Question 8

What are the types of humoral immunity?

Answer 8

Active (lasts years)

Passive (lasts weeks)

Question 9

What are examples of passive humoral immunity?

Answer 9

1. natural immunity: mother – fetus/baby across placenta, milk
2. artificial immunity: artificially produced antibodies (from another person, animal or monoclonal) are injected
   ~> examples: tetanus, rabies, snake bite antivenins, Rh factor
   ~> mops up antigen before it can trigger an immune response in
   person

Question 10

Explain active immunity

Answer 10

Body makes antibodies, memory B cells, after:
i. exposure to pathogen = natural immunity; or
ii. injection with killed/inactivated pathogen (vaccination) = artificial immunity

Question 11

Helper T-cells release chemicals that may activate what?

Answer 11

a) Cytotoxic T-Lymphocytes – which proliferate & destroy either:
- virus-containing cells;
- cells altered by cancer; or
- cells from transplanted organs
= Cell Mediated Immunity

b) B cells – which proliferate and convert to plasma cells that produce antibodies
= Humoral (Antibody Mediated) Immunity

Question 12

What happens in the immune response?

Answer 12

a) Phagocyte (e.g. macrophage) “eats” invader and displays parts of it (Ag) on its surface
b) Helper T-cell binds to antigen-phagocyte complex and is activated. Activation causes it to proliferate and produce more HTC
> releases:
- Cytotoxic T-Lymphocyte
- B cells
- memory B/T cells

Question 13

What is the principle difference between innate and adaptive defenses?

Answer 13

Innate defenses are for immediate, non-specific protection

Adaptive defenses are for long-term, targeted responses

Question 14

What do natural killer cells do?

Answer 14

They are a type of lymphocyte that can non-selectively kill cancer cells
and virus-infected body cells

Question 15

In general terms, what are innate defenses?

Answer 15

They prevent entry of microbes into body or remove foreign material. It consists of surface barriers and innate internal defenses that act as the first and second lines of defense respectively