Cell recognition/Immunity 3.2.4

Question 1

What are 3 features of the non-specific immune system?

Answer 1

• The response is immediate.
• The response is the same for all pathogens.
• The response involves physical barriers and phagocytosis.

Question 2

What are 3 features of the specific immune system?

Answer 2

• The response is slower.
• The response is specific to each pathogen.
• The response involves lymphocytes.

Question 3

What must lymphocytes be able to do?

Answer 3

• Distinguish between self and non-self material.

Question 4

What are the proteins on the surface of cell membranes that are able to detect foreign material called?

Answer 4

• Antigens.

Question 5

What is a phagocyte?

Answer 5

• A type of white blood cell which carries out phagocytosis.

Question 6

What is phagocytosis?

Answer 6

• Mechanism by which cells engulf a pathogens to form a vesicle.

Question 7

Outline phagocytosis in 6 steps…

Answer 7

1) Phagocyte is attracted to a foreign chemical left behind
2) Phagocyte attaches to chemicals on the surface pf the pathogen via receptors.
3) Cytoplasm of the phagocytes moves around the pathogen and engulfs it causing a phagosome to be produced.
4) A lysosome fuses with a phagosome, releasing lyzozymes enzymes into phagosomes.
5) Lyzozymes hydrolyse the pathogen.
6) Phagocyte presents pathogen’s antigens on its surface.

Question 8

What are 3 features of T lymphocytes?

Answer 8

• Made in the bone marrow.
• Matured in the thymus gland.
• Involved in the cell mediated response.

Question 9

What are 3 features of B lymphocytes?

Answer 9

• Made in the bone marrow.
• Matured in the bone marrow.
• Involved in the humoural response.

Question 10

Outline the cell-mediated response in 4 steps…

Answer 10

1) Phagocytosis occurs
2) Phagocyte presents antigens on its surface.
3) T helper cells bind to the antigen via specific T-cell receptors.
4) The binding activates T helper cells to divide rapidly by mitosis.

Question 11

What cells do T helper cells produce?

Answer 11

• Memory B cells
• Stimulate phagocytes to engulf pathogens by phagocytosis
• B cells
• Cytotoxic T cells.

Question 12

What is the role of cytotoxic T cells?

Answer 12

• To kill abnormal cells and body cells infected by pathogens.

Question 13

How do cytotoxic T cells kill abnormal cells?

Answer 13

• By producing perforin, a type of protein.
• Perforin makes holes in the membrane allowing full permeability causing cells to die.

Question 14

What is an antibody?

Answer 14

• A protein produced by B lymphocytes in response to the presence of the antigen.

Question 15

Outline the humoural response in 7 steps…

Answer 15

1) Surface antigens of an invading pathogen are taken in by endocytosis.
2) B cells process antigens and present them on cells.
3) T helper cells attach to receptors on the APC B cell to activate it.
4) B cells divides by mitosis (clonal selection) to produce plasma cells.
5) Plasma cells are produced which create antibodies specific to the antigen on the pathogen’s surface.
6) Antibody-antigen complex is formed causing agglutination, making it easier for phagocytes to engulf pathogens.
7) B cells form memory cells which can rapidly divide into plasma cells.

Question 16

Why is the secondary response more efficient than the primary response?

Answer 16

• Secondary response allows antibodies to be produced at a faster rate.
• Memory B cells can divide rapidly into plasma cells that produce specific antibodies to the antigen.

Question 17

What is a vaccine?

Answer 17

• The injection of an inactive pathogen which stimulates an immune response against a pathogen.

Question 18

Why are vaccines important?

Answer 18

• Vaccines stimulate memory cell production against a disease for the future.

Question 19

What is herd immunity?

Answer 19

• Herd immunity occurs when a large portion of a population becomes immune to a disease, either through vaccination or prior infection.
• thereby reducing its spread and protecting those who are not immune.

Question 20

What is antigenic variability?

Answer 20

• Antigenic variability is the ability of pathogens to alter their surface proteins to evade detection by the host’s immune system.

Question 21

What is active immunity?

Answer 21

• Active immunity is the protection against disease developed by an individual’s immune system after exposure to a pathogen or through vaccination.

Question 22

What is passive immunity?

Answer 22

• Passive immunity is the temporary protection against disease gained by receiving antibodies from another source, such as maternal antibodies or antibody injections, without the immune system generating its own response.