5d: Defence Against Parasitic Attack

Question 1

Non-specific immune defences

Answer 1

Physical barriers, chemical secretions, inflammatory response, phagocytes, and natural killer cells destroying cells infected with viruses are examples of non-specific defences

Question 2

Examples of physical barriers (non-specific defences)

Answer 2

Epithelial tissue blocks the entry of parasites

Question 3

Examples of inflammatory responses

Answer 3

Injured cells release signalling molecules. This results in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes.

Question 4

Examples of phagocytes as non-specific defences

Answer 4

Killing of parasites using powerful enzymes contained in lysosomes, by engulfing them and storing them inside a vacuole in the process of phagocytosis.

Question 5

Example of natural killer cells as non-specific defences

Answer 5

Natural killer cells can identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis.

Question 6

Example of specific cellular defences

Answer 6

• A range of white blood cells constantly circulates, monitoring the tissues
• If tissues become damaged or invaded, cells release cytokines that increase blood flow resulting in non-specific and specific white blood cells accumulating at the site of infection or tissue damage

Question 7

Mammals contain many different lymphocytes, each __________ , which can potentially recognise a parasite antigen

Answer 7

possessing a receptor on its surface

Question 8

Binding of an antigen to a lymphocyte’s receptor selects that lymphocyte to then divide and…

Answer 8

produce a clonal population of this lymphocyte

Question 9

Some selected lymphocytes will…

Answer 9

Some selected lymphocytes will produce antibodies or others can induce apoptosis in parasite-infected cells

Question 10

Antibodies possess regions where…

Answer 10

the amino acid sequence varies greatly between different antibodies

This variable region gives the antibody its specificity for binding antigen

Question 11

When the antigen binds to this binding site the antigen-antibody complex formed can result ______1_______, rendering it ______2______ , or can ______3_______

Answer 11

1. In inactivation of the parasite
2. susceptible to a phagocyte
3. stimulate a response that results in cell lysis

Question 12

Initial antigen exposure produces…

Answer 12

• memory lymphocyte cells specific for that antigen that can produce a secondary response when the same antigen enters the body in the future.
• when this occurs antibody production is enhanced in terms of speed of production, concentration in blood and duration

Question 13

Example of chemical secretions (non-specific defences)

Answer 13

• hydrolytic enzymes in mucus, saliva and tears destroy bacterial cell walls
• low pH environments of the secretions of stomach, vagina and sweat glands denatures cellular proteins of pathogens.