Parasitism (d) Defence Against Parasitic Attacks

Question 1

Immune response in mammals has both…

Answer 1

Non-specific and specific aspects

Question 2

Non-specific defences include:

Answer 2

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

Question 3

Physical barriers include:

Answer 3

Epithelial tissue which block the entry of parasites;hydrolytic enzymes in mucus, saliva and tears that destroy bacteria cell walls; low pH environments of the secretions of stomach, vagina ans sweat glands which denature tthe cellular proteins of pathogens.

Question 4

Inflammatory response involves…

Answer 4

1. Injured cells release signalling molecules. 2. Signalling molecules enhance blood flow to the site, bringing antimicrobial proteins and phagocytes.

Question 5

During phagocytosis…

Answer 5

1. Parasites are engulfed by phagocytes and stored inside a vacuole. 2. The parasites are killed using powerful enzymes contained in lysosomes.

Question 6

Role of natural killer cells:

Answer 6

1. Natural killer cells can identify and attatch to cells infected with the virus. 2. Natural killer cells then release chemicals that lead to cell death by inducing apoptosis

Question 7

Specific cellular defences include:

Answer 7

1. A range of white blood cells constantly circulate, 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.

Answer 8

2. Mammals contain many different lymphocytes, each possessing a receptor on its surface, which can potentially recognise a parasite antigen.

Answer 9

3. Binding of an antigen to a lymphocyte’s receptor selects that lymphocyte to then divide and produce a clonal population of this lymphocyte. Some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite-infected cells

Answer 10

4. Antibodies possess regions where the amino acid sequence varies greatly between different antibodies. This variable region gives the antibody its specificity for binding antigen. When the antigen binds to this binding site the antigen-antibody complex formed can result in inactivation of the parasite, rendering its susceptible to a phagocyte, or can stimulate a response that results in cell lysis. Memory lymphocyte cells are also formed.

Question 11

Memory lymphocytes are also formed. These steps are:

Answer 11

1. Initial antigen exposure produces memory lymphocyte cells specific for that antigen. 2. These memory lymphocyte cells produce a secondary response when the same antigen enters the body in the future. 3. The secondary responses result in enhanced antibody production. 4. Speed of antibody production is faster, concentration in blood increases and their duration is longer.