Biology Topic 6.3

Front 1

What are 4 non - specific responses to infection

Back 1

Lysosomes

Inflammation

Phagocytosis

Interferons (virus)

Front 2

How do lysozyme respond to infection

Where can lysozymes be found?

Back 2

The lysozyme kill bacteria by breaking down cell walls.

They can be found on saliva, nasal secretions - protecting the body from harmful bacteria in the air we breathe or food we eat

Front 3

How does inflammation respond to infections

Back 3

● It helps to destroy invading microbes. Damaged WBCs and mast cells release histamines.

●The histamines cause the arterioles in the area to dilate and increase blood flow in the capillaries at the infected site

●Histamines increase the permeability of capillaries, so plasma, WBCs and antibodies leaks out to the blood stream causing oedema (swelling).

●The infecting microbes can now be attacked by these intact white cells

Front 4

How do phagocytes fight non-specific infections

Back 4

●Phagocytes are white blood cells that engulf bacteria and other foreign matter.

●Phagocytes contain neutrophils and macrophages. Neutrophils injest and destroy bacteria

●Macrophages engulf bacteria, foreign matter and cell debris

Front 5

Explain how a macrophage/ nucleophil engulf bacteria?

Back 5

1) Bacteria with antigens on the surface is engulfed by the macrophage/ nucleophil

2) The bacteria is enclosed in a vacuole.

3) Lysosomes fuse with vacuole releasing enzymes that destroy foreign material.

Front 6

In spite of intense phagocytic activity some bacteria gets carried into the blood. How is the spread of bacteria prevented?

Back 6

They are prevented by the action of macrophages in the lymph nodes, spleen and liver.

1) Tissue fluid drains into lymphatic vessels

2) The fluid called lymph passes through lymph nodes any pathogens present activate lymphocytes and macrophages which can destroy microbes.

Front 7

What are interferons and how do they work?

Back 7

They provide non-specific defence against viruses.

It prevents the viruses from multiplying and inhibits viral protein synthesis and limits the formation of new virus particles

Front 8

What are B cells?

Back 8

●B cells secrete antibodies in response to antigens that act as labels allowing phagocytes to recognise and destroy the cell.

● Each b cell produces only one type of antibody, which means it binds to only one specific antigen

Front 9

How B cells work?

Back 9

1) B cells produce antibodies that bind to antigens and label them

2) The antibody binds to the antibody receptors on macrophage.

3) The macrophage engulfs antibodies and bacterium

4) Lysosomes fuse with vacuole, releasing digestive enzymes that destroy the bacterium

Front 10

What are T cells?

Back 10

They are produced in the bone marrow but they mature thymus gland.

T cells have an antigen receptor on their surface. This only binds to an antigen with the complementary shape.

Front 11

What are two types of T cells?

Back 11

T-helper cells - when activated these stimulate the B cells to divide and become capable of producing antibodies and enhance the activity of phagocytes.

T-killer cells - destroy any cells with antigens on their surface membrane that are recognised as foreign. This includes body cells are infected with pathogens. This also includes tissues received as transplant from another person.

Front 12

Describe the activation of T cells

Back 12

1) Bacteria with antigens on their surface are engulfed by a macrophage.

2) The macrophage presents antigens on its surface to alert the body of foreign material in the body and becomes an APC

3) The APC binds to a T helper cell with complementary shaped receptors called CD4 receptors.

4) Once activated it divides to produce a clone of T- helper cells and T memory cells.

Front 13

Why are T - memory cells useful?

Back 13

● Because they remain in the body for years/ months

● This means that if the individual is exposed to the same antigen in the future, their immune system responds more quickly.

Front 14

Describe the cloning of B cells

Back 14

1) Bacterium with antigens on surface binds to a B cell with complementary receptor, making B cell an antigen presenting cell

2) Activated T helper cells with complementary receptors binds to APC and produces cytokines that stimulate B cells.

3) The B cells divides to give B memory and B effector cells

Front 15

What are the differences between b effector cells and b memory cells

Back 15

B Effector cells - are short lived and differentiate into plasma cells. The plasma cells secrete antibodies which bind to antigens to make them easier to identify for destruction.

B Memory cells - they are longer lived and remain in body for months and years enabling an individual to respond to the same antigens in the future

Front 16

Describe how T killer cells works

Back 16

1) The bacterium infects the host cell and the cell presents antigens and becomes an APC

2) T killer cells with complementary receptors binds to the APC

3) This produces active and memory T killer cells. The active T killer cells bond to the infected APCs.

4) The T killer cells releases chemicals that cause pores to form in the infected cells, causing lysis.

5) Once the the infected cell dies the pathogens are released and once out can be labelled by antibodies from B cells which can then be destroyed by macrophages.

Front 17

Why is the secondary immune response faster than the primary immune response?

Back 17

● Because it uses memory cells and takes 2-7 days.

● The B memory cells can differentiate immediately to produce plasma cells which release antibodies. There is a greater proportion of antibodies and the response lasts longer.

● So invading viruses or bacteria are destroyed rapidly before any symptoms are shown.

Front 18

How do cells avoid attack by our own immune system?

Back 18

● Some membrane proteins on the surface of our bodies act as bar codes. These proteins mark our body cells as 'self'.

● They allow us to distinguish between our own cells and foreign invaders