The immune system HBS3B. Revision question Using a diagram, explain the structures that comprise a synovial joint and their functions.

The immune system

HBS3B

Revision question

Using a diagram, explain the structures that comprise a synovial joint and their functions.

Synovial joints• Synovial capsule surrounds the

joint and helps stabilise it and hold it all together

• Synovial membrane is thin and smooth, to reduce friction, and secretes synovial fluid

• Synovial fluid is thick and sticky, and acts as a lubricant for the joint

• Articular cartilage provides a smooth surface to reduce friction as the bones move across each other

• Articular disc are cartilaginous discs which act as shock absorbers

• Bursae are fluid filled sacs which act as shock absorbers

• Accessory ligaments join the bones and keep them together

The nervous and endocrine systemsLabel the structures

List the hormones and their effects

The nervous and endocrine systemsLabel the structures

List the hormones and their effects

cerebrum

cerebellum

hypothalamus

pons

pituitary gland

medulla

spinal cord

The immune responseThe specific protection the body

has against a particular pathogen or foreign chemical results from a process called the immune response

There are two components of the immune response – the humeral or antibody mediated response and the cell mediated response

Both rely on the recognition of antigens.

An antigen is anything that triggers an immune response. Most antigens are proteins, and are either toxins, protein coats around viruses, or parts of cell walls or membranes. These act like labels that the white blood cells can read to tell whether it belongs in the body or not.

The immune response

Humeral responseThis response involves B-

lymphocytes or B-cells.This response provides

resistance to bacteria, viruses and bacterial toxins

B-cells detect free antigenHelper T-cells detect

macrophage-presented antigens and stimulate B-cells

The B-cells then begin to divide or clone

Two types of B-cells are then produced –

Plasma cells make free antibody

Memory cells store information about antigen for future response (immunity)

AntibodiesAntibodies are specific for particular

antigens. This means that they fit the antigen like a

lock an keyAntibodies work by attaching to an

antigen and:• preventing viruses from entering cells

• inactivating toxins• destroying cell walls• causing agglutination• reducing solubility• attracting white blood cells• increasing phagocytosis• activating complement

Phagocytosis

Macrophages engulf and destroy foreign invaders. This process is made easier when the pathogen is coated with antibody

Cell mediated responseThis response involves T-lymphocytes

or T-cells.This response provides resistance to

intracellular phase of bacteria and viruses as well as resistance to fungi and parasites, rejection of transplants and fighting cancer cells

T-cells detect free antigenHelper T-cells detect macrophage-

presented antigens and stimulate other T-cells

The T-cells then begin to divide or cloneFour types of B-cells are then produced

–Helper cells aid in recognition and

activate other lymphocytesKiller-cells (cytolytic cells) produce

cytotoxic chemicals which kill foreign cells

Memory cells store information about antigen for future response (immunity)

Suppressor cells stop the immune process when the antigen has been removed

Specific versus non-specific responsesSpecific defences The immune response is said to be

specific, because it only responds to a specific antigen.

Each pathogen carries a certain marker (usually proteins) or has a certain shape - this is called an antigen.

The lymphocytes recognise the antigens on its own body cells as self.

Any other antigens are foreign, and to be destroyed.

The immune response produces antibodies and killer lymphocytes targeted against one, and only one, antigen.

This usually results in the destruction of this antigen, and a memory, or immunity, for this particular antigen, due to the presence of memory cells (both B and T cells).

Each new antigen must be recognised, and a new set of antibodies and killer t-cells manufactured against it.

Non-specific defencesNon specific responses react to any pathogen. They include external defences including physical

barriers & traps • skin - water proof, impermeable barrier, • mucous membranes – barrier, mucus, • ear wax - sticky trap, hairs - trap pathogens, • cilia in respiratory tract - catch & move

pathogens up to pharynx where they are swallowed,

• tears, sweat, urine - wash away pathogens chemical traps & protection • lysosome - enzyme in tears kills bacteria, • cerumen - enzyme in ears kills bacteria, • sebum - enzyme on skin kills bacteria, • acidic secretions in stomach, urine, vagina

prevent growth of pathogens, digestive • enzymes in saliva, stomach & intestine kill

bacteria), friendly bacteria on skin prevent pathogens from

multiplying,Internal protection includes inflammation and non-

specific phagocytosis.

Immunity

Immunity is protection from disease due to presence of antibodiesActive immunity – have memory cells and can make own antibodiesPassive immunity– have antibodies, but not memory cells so can’t

make own antibodies (antibodies come from someone else)Natural immunity– no human intervention is required, Artificial immunity– human intervention is required.Active Natural – get disease and make memory cells. Active artificial – vaccination to stimulate memory cell production Passive natural – antibodies pass from mother to baby (via placenta

or milk). Passive artificial – given injection of antibodies/antitoxins. .

Vaccination

Immunization or vaccination depends on using an antigen prepared in a relatively harmless form as the primary stimulus to develop immune memory (ie presence of memory cells). If the person is subsequently infected they have the ability to produce large amounts of antibody very quickly.

The ready made anti toxins or antibodies used to provide passive immunity in humans are usually made by injecting an animal (usually horses) with antigen, then collecting the blood and taking out the antibodies they made.

This provides passive immunity that lasts for a short time.Vaccines are preparations of antigens used to stimulate the immune system.There are four main types of vaccines:i) living attenuated – pathogen weakened by giving to other animals/growing in

tissue culture eg measle, mump, polioii) dead microorganisms – pathogen killed by heat/radiation eg cholera, typhoidiii) toxoids – fake/inactivated toxin eg cholera, typhoidiv) Sub-units -antigens made by recombinant DNA (genetic engineering) –

antigen only so no possibility of getting disease eg Human papilloma virus, hepatitis B

Vaccines

Some problems seen with vaccinations are side effects eg allergic reactions, people actually getting the disease, and short effectiveness of some older vaccines so re-immunisation is needed.

Methods used to reduce the virulence or possibility of side effects of vaccines are to use recombinant DNA technology to reduce virulence of pathogens in a vaccine, or to produce vaccines containing harmless bacteria genetically engineered to produce the antigen or only the antigen (not the whole pathogen).

Vaccines can be delivered by a number of methods including injection, by mouth, by nasal spray, by skin patches.

A new area of research is genetically engineered plants to act as vaccines.

Herd immunity refers to immunity levels within a population. If enough people are immune (through natural or acquired immunity) disease transmission is slowed.

Some risks and concerns about the production of vaccines include the side effects (eg allergic reactions), the risk of cross species disease introduction and effects of preservatives or added chemicals in the vaccines.

Some people choose not to be vaccinated or have their children vaccinated because of concerns about these risks, religious beliefs or ignorance about the benefits of vaccination or prevalence of the disease being vaccinated against.

Primary and secondary response

What happens to the amount of antibody in the blood in response to an initial attack by a pathogen?

This initial increase is called the p_________ response.Describe what happens, at a second pathogen attack, to the amount of antibody.

Compare this secondary response with the primary response.

Why does a second infection result in a quicker and stronger response?

Explain why booster doses of vaccines are needed in some immunization schedules

Primary and secondary response

What happens to the amount of antibody in the blood in response to an initial attack by a pathogen? It takes ~7 days to respond, then increases over 10 days, before gradually falling

This initial increase is called the primary response.Describe what happens, at a second pathogen attack, to the amount of antibody. It takes

~3 days to respond, then increases more rapidly and to a higher level, and its fall is lower.

Compare this secondary response with the primary response. Its faster and stronger & the fall is less

Why does a second infection result in a quicker and stronger response? There are memory cells present, so recognition and response is faster

Explain why booster doses of vaccines are needed in some immunization schedules Over time antibody levels fall. If they fall to far you will not have enough antibodies to protect you from the disease. A booster stimulates more lymphocytes & a higher antibody level

Antibiotics and antivirals Antibiotics are chemicals that kill bacteria or other microbes. They work by

destroying cell structures or interfering with metabolic processes.Examples include penicillin, amoxicillin, streptomycinAntibiotics are only effective against bacteria (and some protozoa and fungi)Viruses are not affected by antibiotics as they are not cells, therefore can not

be affected by chemicals that destroy cell structures or functioning.

One problem with antibiotic use is antibiotic resistance. This is a problem because bacteria that were once considered harmless are now capable of causing serious disease or death, as they are not killed by commonly used antibiotics.

Some reasons why resistance is increasing include overuse of antibiotics in

medicine (eg for treating viral infections) and agriculture (especially in food animals) and people not finishing the course of antibiotics they were given when sick

Viral diseases can be treated by chemicals called antiviralsExamples include zidovudine (AZT) and interferon.These act by interfering with the virus’s ability to invade cells or increasing the

immune systems effectiveness