Immunity

Question 1

What do each type cell have on its surface and why

Answer 1

• They have specific molecules on its surface
• these molecules include proteins + enable the immune system to identify: pathogens, toxins, abnormal body cells,cells from other organisms of the same species

Question 2

What is an antigen

Answer 2

• Foreign protein
• usually a protein molecule
• that stimulates an immune response

Question 3

What is the effect of antigen variability

Answer 3

• The structure and shape of the antigen can change due to random mutations in the genetic code of a pathogen
• so any previous immunity to this pathogen is no longer effective as all the memory cells in the blood doesn’t recognise the antigens as it will have memory of the old antigen shape

Question 4

Disease prevention- why do vaccines like the flu needs to be re-administered regularly

Answer 4

-It is easier to develop vaccines of pathogens with no antigen variability than those with high antigen variability
-as antigens on the surface change shape regularly
-as higher antigen variability contain several different strains

Question 5

What is a phagocyte

Answer 5

A macrophage which is a type of white blood cell that engulf and destroy pathogens

Question 6

What is phagocytosis

Answer 6

It is a non-specific response to an invading pathogen that has entered the body and destroys it

Question 7

What is the phagocytosis process

Answer 7

-phagocyte recognises foreign antigens on a pathogen
- The receptors on the surface of phagocyte attaches and becomes complementary to the antigens of pathogen
- phagocyte changes shape and engulfs the pathogen in a phagosome vesicle
- lysosomes fuses with the phagosome and release it’s contents
-The lysozyme enzyme is released in the phagosome which hydrolyses and breaks down the pathogen and is destroyed

Question 8

What are the 2 types of lymphocytes

Answer 8

T-lymphocytes(T cells)
B-lymphocytes(B cells)

Question 9

What is a T lymphocyte (T cells)

Answer 9

• White blood cells In the specific immune response
  -these mature in the thymus gland
• associated in the cell-medicated response

Question 10

Why is the cellular response specific

Answer 10

T cells respond to antigens on its surface

Question 11

What is en antigen presenting cell

Answer 11

Any cell that presents a non- self antigen on its surface

Question 12

What T cells are involved in the cellular response

Answer 12

Helper T cells and cytotoxic T cells

Question 13

Describe the cellular response

Answer 13

-pathogens invade the body and are engulfed by phagocytes
-a special type of phagocyte becomes an antigen presenting cell by inserting the pathogens antigens into its cell surface membrane
-helper T cells have receptors on its surface and can become complementary to the Antigens on the APC
-this activated the helper T cells to divide by mitosis to replicate and make more clones- clonal selection
-the cloned helper T cells differentiate into: phagocytes to engulf more pathogens,stimulate B cells, some become memory cells and cytotoxic T cells

Question 14

What is the function of cytotoxic T cell

Answer 14

-they destroy abnormal or infected cells
-they release a protein which imbeds in the cell surface membrane to make a pore so that substances can move in and out to cause deaths ie burst or shrivel out

Question 15

What is a B lymphocyte

Answer 15

-these are white blood cells and are associated with humoral immunity
-these mature in the bone marrow

Question 16

Describe the humoral response

Answer 16

• antigens of pathogen in the blood are taken up by B cells
  -the B cells then present the antigens on their cell surface membrane
  -the B cells divide by mitosis and undergo clonal expansion and differentiate into short lived plasma cells and memory cells
  -the plasma cells produce antibodies complementary to the antigens
  -and attach to antigens on pathogen leads to the destruction via agglutination and phagocytosis-primary immune response
  -the memory cells stay in the bloodstream and once they come into contact with the antigen again they divide into B memory cells +B plasma cells-secondary immune response

Question 17

What are the 2 B lymphocytes(B cells) involved in the humoral response

Answer 17

Memory cells and plasma cells

Question 18

Compare the primary immune response and secondary immune response

Answer 18

Secondary:
-faster rate of antibody production
-higher concentration of antibody production
-long lived
Primary
-slower rate of antibody production
-lower concentration of antibody production
-relatively short lived

Question 19

Define an antibody

Answer 19

• a protein(quaternary structure) produced by B cells and secreted by plasma cells

Question 20

What is the antibody structure

Answer 20

-composed of 4 polypeptide chains- 2 heavy chains and 2 light chains
-these chains are arranged in a Y shape held by disulphide bridges
-tips of antibody form the antigen binding site-each tip has a variable region formed by amino acids that produce specific 3D Shapes-allows to bind to diff complementary antigens
-has a constant region
-receptor binding site enables an antibody to attach to cell surface membrane to form antibody complexes

Question 21

How does the formation of an antigen antibody complex leads to the destruction of the antigen/pathogen

Answer 21

-antibody has 2 binding sites so it can bind to 2 pathogens at the same time
Means pathogens clump together-agglutination making it easier to locate so phagocytes bind to antibodies and engulf pathogen so destroy it

Question 22

What is the role of plasma and memory cells in producing primary and secondary immune responses

Answer 22

Primary immune response:
-plasma cells produce antibodies but only survive in the blood stream for a few days
-also produce memory cells that stay in the bloodstream for a much longer time
-when the antigen is encountered again memory cells divide rapidly into plasma cells and memory cells which forms a secondary immune response
Secondary immune response
- plasma plus produce antibodies to destroy the pathogen much more rapidly
-memory cells enter the blood to provide long term immunity

Question 23

Describe the differences between active and passive immunity-

Answer 23

-active involves memory cells passive does not
-active involves the production of antibodies by plasma/memory cells
-passive involves antibody introduced from the outside
-active is long term bc antibody produced in response to antigen
-passive is short term as antibody is broken down

Question 24

How is the use of vaccines used to provide protection for individuals and populations against disease

Answer 24

-small amounts of dead or weakened pathogen or antigens are introduced in the mouth or by injection that triggers immune system
-exposure to the antigens activated the B cells to go through clonal expansion or differentiation( clonal selection)
-b cells divide by mitosis to make large numbers of cells-these differentiate into plasma or memory cells
-plasma cells make antibodies
-when someone is re infected by the pathogen plasma produce antibodies rapidly
-memory cellsprovides a faster immune response later

Question 25

What is herd immunity

Answer 25

If enough people in the population are vaccinated the pathogen cannot spread easily amongst the population
-this provides protection for people who are not vaccinated
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