Week 3 - Innate Immunity

Question 1

Name the three lines of defence

Answer 1

• First line
• Second line
• Third line

Question 2

What type of defence is First-line defence?

Answer 2

Innate/non-specific

Question 3

What is the aim of first-line defence?

Answer 3

To prevent a vide variety of microorganisms from entering the body

Question 4

What type of defence is second-line defence?

Answer 4

Innate/non-specific

Question 5

What is the aim of second-line defence?

Answer 5

Defences which help to eliminate a wide variety of microorganisms which have penetrated the body (fever, inflammation)

Question 6

What type of defence is third-line defence?

Answer 6

Acquired/specific

Question 7

What is the aim for third-line defence?

Answer 7

Helps to eliminate specific microbes which have penetrated the body and protect the host against future attack by the same organism.
(Called acquired / adaptive because they develop as a result of contact with the microbe)

Question 8

Name the cells involved in phagocytosis

Answer 8

• Macrophages,

- Monocytes,

Question 9

What is the function of phagocytosis?

Answer 9

• Both monocytes & macrophages devour pathogens, damaged tissue cells & dead neutrophils,
• Elimination of pathogens, cell debris and apoptotic cells

Question 10

State the overall functions of inflammation

Answer 10

• Destroy the microbe (& its by-products).
• Prevent the spread of the microbe (by building a wall of fibrin around it so it is confined to a local area).
• Clear the site of cellular debris and dead microbes
• Repair the damaged tissue.

Question 11

Name the three stages of inflammation

Answer 11

• Vasodilation and increased blood vessel permeability
• Phagocyte migration and phagocytosis
• Tissue repair

Question 12

Describe ‘Vasodilation and increased blood vessel permeability’

Answer 12

When tissue is damaged, basophils and mast cells in the area are stimulated to release histamine and prostaglandins. Histamine diffuses to local blood capillaries and causes them to dilate and become more permeable. Dilation increases the blood flow in the damaged area resulting in increased delivery of WBC, clotting factors, nutrients and removal of wastes. Clotting factors enable the resultant fibrin mesh to trap microbes and prevent spread to other tissues

Question 13

Describe ‘Phagocyte migration and phagocytosis’

Answer 13

Phagocytes are attracted by chemicals released in stage 1 and from the microbes. Neutrophils and monocytes squeeze between the cells lining the blood vessels. Monocytes become active macrophages. Both monocytes and macrophages devour pathogens, damaged tissue cells and dead neutrophils - a process called phagocytosis

Question 14

Describe ‘Tissue repair’

Answer 14

This begins once all microbes, foreign material, damaged tissue and pus have been removed from the area. If the damage is minor then cells are replaced by mitosis. If tissue is incapable of regeneration (nerve tissue) or is extensively damaged, scar tissue forms

Question 15

What are some signs of inflammation?

Answer 15

• Redness
• Heat
• Swelling
• Pain
• Loss of function (sometimes)
• Puss occurs with nearly all infections and inflammatory responses but is not always a visible sign

Question 16

What are some signs and symptoms with the first inflammatory response? (Vasodilation and increased blood vessel permeability)

Answer 16

• Heat and redness (due to increased blood supply)
• Oedema caused by increased permeability of capillaries allowing leakage of plasma into the interstitial space
• Pain can result from::
  - Injury
  - Oedema which causes pressure on the
  wound
  - Irritation by toxic chemicals from microbes
  and release of prostaglandins (initiate pain
  response) to stimulate pain receptors

Question 17

What are some signs and symptoms with the second inflammatory response? (Phagocyte migration and phagocytosis: FORMATION OF PUS)

Answer 17

• Pus is a thick, creamy-coloured fluid containing dead phagocytes, damaged tissue cells and bacteria
• Abscesses, pimples and boils are accumulations of pus in a confined space walled off by fibrin.
• This localises the infection and toxic substances released from dying cells

Question 18

What colour is pus and what does it contain?

Answer 18

Thick, creamy-coloured fluid containing dead phagocytes, damaged tissue cells and bacteria

Question 19

What are some signs and symptoms with the third inflammatory response? (Tissue repair: SCAR TISSUE)

Answer 19

• Consists mainly of collagen
• Is used to repair extensive wounds
• Does not have the functions of the damaged tissue, but it does fill the damaged area

Question 20

Describe the role of fever in the inflammatory response

Answer 20

• Temperature-regulating centre in the hypothalamus controls the body’s internal temperature
• The hypothalamus initiates heat-raising mechanism like shivering and constricting dermal blood vessels, so the skin (and the person) feels cold - causing symptom of chills
• Body temperature remains high until the infection subsides and the level of pyrogens (presence of chemicals) decreases
• The body temperature is rest to 37 degrees Celsius and the hypothalamus initiates cooling mechanisms like sweating and vasodilation

Question 21

What are some implications of treating a fever? (eg. what situations would you and would you not treat?)

Answer 21

• Tachycardia which may compromise older people with cardiopulmonary disease or very young persons
• Increased metabolic rate may cause acidosis
• Dehydration and electrolyte imbalances may result
• Febrile convulsions in young children
• Delirium and coma if complications not detected and treated promptly
• Death results if fever rises above 44 - 46 degrees Celsius

Question 22

What are some benefits of a fever?

Answer 22

• Raises the temperature above the optimal temperature for growth of many pathogens so slows rate of bacterial growth.
• Makes the person feel ill so they rest & have energy to fight the infection.
• The body’s defence mechanisms are faster & the duration of the infection is shorter.
• Speeds up the body’s reactions to enhances tissue repair