The Immune System

Home Team: Immunity Away Team: The Pathogens

Natural Immunity• The immune system can distinguish between

our body and foreign material• Our immune system ‘fights’ infection through

specific and non specific responses.:

Non-specific Responses:• React the same way to all infections• Have no memory of previous infection• The level of response is the same for each

infection/exposure to the same pathogen• First and second lines of defence

Specific Responses: • React in a specific way to each infection• Have a memory of previous infection• Much greater response for second or subsequent

infections/exposures to the same pathogen• Third line of defence

Group Activity

• You are a group of students defending a circle on the ground. No one must enter this circle.

• You have heard the enemy is coming• Come up with as many strategies as you can to

keep them out of your circle• You have 5 minutes

First Line of Defence• Non-specific Immune Response and involves:

• Skin – prevents pathogens entering the body• Scabs – form to prevent pathogens entering the body through

breaks in the skin• Acids – e.g. in the stomach and vagina, can kill some pathogens• Enzymes – such as lysozyme in our tears and saliva, can kill some

pathogens• Mucous and Cilia – can trap pathogens in the upper respiratory

tract and carry them to the stomach• Learned Behaviours – such as washing hands and covering our

cough, or avoiding sick people can prevent infection

Group Activity

• You are a group of students defending a circle on the ground. The enemy has entered the circle.

• You have combat training• Come up with as many strategies as you can to

get them out of your circle• You have 5 minutes

Second Line of Defence

• This is a Non-Specific Response and involves:

• White Blood Cells– Phagocytes engulf and destroy micro-organisms

and other foreign materials, this is known as Phagocytosis (refer to Blood and Heart Notes from term 1). Include neutrophils and monocytes.

– Natural Killer (NK) Cells are white blood cells that kill virus infected cells

• Complement Proteins–Assist in a number of ways• Stick to invading micro-organisms to

allow them to be quickly recognised by phagocytes. • Attract more phagocytes to the site of

infection• Destroy the membranes of invading

micro-organisms

• Interferon– Are proteins secreted from some cells when they

are infected by virus particles. – Act on uninfected cells by making them more

resistant to the virus.– Early response and can help us resist/prevent

some viral infections. • Fever– Proteins in blood called Pyrogens increase body

temperature which inhibits microbial multiplication and enhances the body’s repair processes

• Inflammation– Prevents the spread of damaging agents to nearby

tissues by forming blood clots to ‘wall’ of area– Disposed of debris and pathogens by increasing

the number of white blood cells to the area– Sets the stage for repair processes– Symptoms include: Heat and Redness (increased

blood flow to the area), Pain and Swelling (leaky vessels allow white blood cells and other proteins, like clotting factors, to enter tissues)

Individual Activity

• Read pages 302-306 of Biology 2 text• Answer questions 2-7 on page 306

The third line of defence• Involves a specific response by the immune system to a

particular infection.• Two main groups of lymphocytes (type of white blood

cell) are involved in fighting the infection.• All lymphocytes are produced in bone marrow.• Some mature in the bone marrow into B lymphocytes or

B cells.• Others leave the bone marrow and

mature in the thymus gland into T lymphocytes or T cells.

Identifying foreign material• All cells have protein markers on their surfaces.• These markers are determined by genes called

the major histocompatibility complex (MHC)• B cells and T cells recognise and ignore ‘self’

markers. They recognise and react with ‘non-self’ markers.

• The marker that triggers a response from a B cell or a T cell is called an antigen (e.g. a virus protein coat or molecules of bacterial toxin).

B cells

• B cells have antibodies on their surface• Antibodies attach to antigens• The antibody of a B cell recognises and binds

to only one kind of antigen• Initially the body produces lots of different

kinds of B cells with a different antibody on their surface

Please draw Figure 16.1, p. 133

Antibody production

• When an antibody recognises and binds to an antigen the B cell carrying that antibody reproduces lots of special cells called plasma cells and a few B-memory cells• Each plasma cell produces lots of the

particular antibody and releases it into body fluids

Recovery

Once antibodies of the right shape have been made in sufficient numbers, the invading organism is killed in one of a variety of ways. The antibody may:

1. cause the micro-organism to agglutinate (clump) so neutrophils can eat them

2. detoxify poisons produced by the pathogen3. cause the micro-organism’s cell membrane

to collapse

Immunity• People take time to recover because it takes

time for the B-lymphocytes to clone plasma cells and for the cloned cells to produce enough antibody

• Some B-lymphocytes produce B-memory cells which will recognise the pathogen next time it invades and cause much quicker antibody production and so the person may never again suffer from the disease.

• The person is said to have natural active immunity.

How much antibody is produced?

In what ways does the secondary antibody response differ from the primary antibody response?

Class Activity

Antibody Mediated Immunity

T cells• Many different kinds of T cells are produced which

recognise many different antigens.• Killer T cells kill cells infected by viruses. This stops the virus

multiplying.• Helper T cells help recognise antigens and stimulate B cells. • Memory T cells provide long term immunity in the case that

the virus is encountered again• Both B cells and T cells travel around the body in the

lymphatic system. White blood cells are concentrated in lymphoid tissues, organs and nodes.

The lymphatic system

Individual Activity

• Read pages 313-316 of Biology 2 text• Answer questions 16-19 on page 314

Individual Activity

• Read pages 306-316 of Biology 2 text• Answer questions 8-15 on page 313• Answer questions 16-19 on page 314

Group Activity

• Each group will be given a scenario• Answer the questions and present your

answers to the class

Acquiring Immunity

• Specific immunity is Acquired Immunity (you only develop immunity following exposure. Immunity can be:– Active – antibodies are made in the body– Passive – antibodies are produced in one person

and transferred to another

Acquired Immunity

Active Immunity

Natural

Antibodies made after exposure to infection

Induced

Antibodies made after immunisation with

toxoid or with killed or treated organisms

Passive Immunity

Natural

Antibodies acquired by baby across placenta or in mother’s milk

Induced

Antibodies acquired through injection of

Immunoglobulins (antibodies)

Memory B and T cells No Memory Cells

Read

• Read page 136 of your white book:• The History of Inoculation and Vaccination

against Small Pox

Immunisation

• Vaccination is the process of introducing the vaccine into the body

• Immunisation is the immune response to the vaccine that results in immunity

• Vaccines (dead or live but weakened/attenuated pathogens and synthetic antigens) are used to activate the immune system against that specific disease, without causing the disease. Vaccines have the same antigens as the infective pathogen. Vaccines are usually injected or ingested.

• Vaccination:– Usually involves a series of injections to bring on lasting

immunity. This is the vaccination program and involves:1. A first vaccination, in which the vaccine in introduced into

the body for the first time2. A primary response, during which plasma cells slowly

produce small amounts of antibodies, resulting in short term immunity. Some memory cells are produced

3. A second vaccination, in which a second vaccine (or booster) is introduced into the body. Existing memory cells respond.

4. A secondary response, during which plamsa cells rapidly produce large amounts of antibodies. Further production of memory cells resulting in long term immunity.

• Some pathogens secrete toxins which can be treated with Toxoids in a similar way to vaccines.

• Vaccine preventable diseases include:– Tetanus, Diphtheria, Pertussis (Whooping Cough),

Hepatitis A, Hepatitis B, Varicella Zoster (Chicken Pox), Poliomyelitis, Measles, Mumps, Rubella (German Measles), Influenza, there are many more

Individual Activity

• Read pages 317-326• Answer questions 20-23 on page 322• Answer questions 24-29 on page 326