Topic 2C - Year 1 - Cells and the Immune System - The Immune Response

Question 1

What is a phagocyte?

Answer 1

A phagocyte is a type of white blood cell that carries out an immune response known as phagocytosis.

Question 2

Summarise phagocytosis in a phrase:

Answer 2

Engulfment of pathogens

Question 3

Where are phagocytes found ?

Answer 3

Phagocytes are found in the blood and in the tissues

Question 4

Which cells are the first to respond if an immune response is triggered?

Answer 4

Phagocytes

Question 5

How does a phagocyte work?

Answer 5

Firstly the phagocyte recognises the foreign antigens on a pathogen.

The pathogen and phagocyte are brought closer together due to chemotaxis

The cytoplasm of the phagocyte moves around the pathogen engulfing/ invaginating it. This process is known as endocytosis as it is a but movement into the cell.

The pathogen is now contained in a phagosome

A lysosome which is found inside the phagocyte binds to the phagosome which contains the pathogen to create a phagolysosome .

The lysosome releases its lysozyme’s into the phagolysosome and these powerful hydrolytic enzymes break down the pathogen.

A phagocyte then gets rid of the waste products of the breakdown which are now harmless by process of exocytosis which is blue movement out of the cell

A phagocyte then presents some of the pathogens antigens to act as an antigen presenting cell to activate other immune system cells.

Question 6

How are T cells activated?

Answer 6

T cells are activated when the receptor proteins on their surface bind to complimentary antigens presented on phagocytes.

Question 7

Name two types of T cell

Answer 7

T helper cell

T cytotoxic cell

Question 8

T cells scan also be referred to as?

Answer 8

T lymphocytes

Question 9

What do T helper cells do in the immune response?

Answer 9

T helper cells do not attack the foreign or abnormal cels himself instead they release chemical signals called cytokines . These chemical signals stimulate phagocytes and T cytotoxic cells into killing the abnormal or foreign cells. T helper cells also stimulate B cells.

Question 10

If a T helper cell binds one of the receptor proteins on its surface to a complimentary antigen then what happens?

Answer 10

The T cell begins to replicate itself by mitosis to form many identical cells which carry the complimentary protein that binds to the invading antigen. The process is called clonal selection.

Question 11

What do T cytotoxic cells do?

Answer 11

T cytotoxic cells attach themselves to the antigen of the pathogen or abnormal body cell via their complimentary receptor protein , the T cytotoxic cell then destroys the foreign antigen presenting cell by recreating toxic substances into the cell which price holes in the membrane.

Question 12

How are B cells stimulated ?

Answer 12

B cells can be stimulated by T helper cells as T helper cells release chemical signals to stimulate them. The binding f an antigen with a B cell receptor can also stimulate it into action.

Question 13

What is the surface of B cells covered in?

Answer 13

The surface of B cells are covered with antibodies.

Question 14

What is formed when an antigen binds to an antibody?

Answer 14

An antigen-antibody complex

Question 15

Do all B cells carry the same antibodies?

Answer 15

No each B cell has a different shaped antibody on its membrane so different ones bind to differently shaped antigens.

Question 16

What happens when a B cell is activated?

Answer 16

When a B cell is activated it begins to divide into plasma cells , only the B cell which has complimentary antibodies to the antigens present begins to divide this is called clonal selection.

Question 17

What do plasma cells do?

Answer 17

Plasma cells which are clones of specific B lymphocytes secrete loads of antibodies to specific antigen , theses antibodies are referred to as monoclonal antibodies.

Question 18

What do the antibodies secreted by plasma cells do?

Answer 18

the antibodies secreted by plasma cells attach themselves to the antigens on the surface of the pathogen to form several antigen-antibody complex.

Question 19

How many binding sites does a single antibody have?

Answer 19

1 antibody has 2 binding sites

Question 20

What process can occur due to the presence of two binding sites on a single antibody?

Answer 20

Agglutination - many pathogens can be clumped together as antibodies join to more than one pathogen , phagocytes then bind to the antibodies and phagocytes many pathogens at once.

Question 21

What are antibodies and thus what are they made from?

Answer 21

Antibodies are proteins and are therefore made from chains of amino acids .

Question 22

What does the specificity of an antibody depend on?

Answer 22

The specificity of an antibody depends on its variable region as its the variable region that forms the antigen binding site. Each antibody has a variable region with a unique tertiary structure that is specific to one specific antigen.

Question 23

what is the part of the antibody that is generic in all antibodies referred to as?

Answer 23

The constant regeion

Question 24

How are antibodies held together?

Answer 24

Antibodies are held together by disulphide bridges.

Question 25

Name the two types of immune response?

Answer 25

Cellular

Humoral

Question 26

What is the cellular response?

Answer 26

The cellular immune response is the response the body cells ave to an invasion of foreign or abnormal cells , the cellular response e thus includes the reaction of phagocytes and T lymphocytes.

Question 27

What is the humoral response?

Answer 27

The humoral response includes the production of monoclonal antibodies by process of clonal selection in B cells.

Question 28

What is the primary response?

Answer 28

When a antigen enters the body for a first time it activates the immune system this is called the primary response.

Question 29

Why is the primary response slow?

Answer 29

The primary response is slow as there are not many B cells that can secrete the correct antibody , hence its more difficult to destroy the pathogen.

Question 30

What do both T and B cells produce after being exposed to a antigen ?

Answer 30

Both T and B cells produce memory cells to record the specific antibodies needed to bind to a specific antigen.

Question 31

In the secondary immune response , the immune system produces a quicker stronger immune response , why is this?

Answer 31

In the secondary response clonal selection happens faster . B memory cells are activated and divide into the correct type of plasma which secrete complimentary antibodies to the antigen. The secondary response often gets rid of the pathogen before you start to show any symptoms.