The Human Defence System

Human defence system How do we protect ourselves?

Teacher slide How do we protect ourselves against foreign bodies that cause disease (pathogens)? Possible answers: Antibodies, WBC, immune system Vaccines Antibiotics / drugs

How do I stop you? How do I get in?

Teacher slide How does the baterica / virus / foreign body get into our bodies?(and what do we have to stop it) Through: Skin: physical barrier & sebaceous glands - oil Cuts / wounds: clots / scabs Eyes : tears lysozyme enzyme dissolves cell walls Mouth: lysozyme in saliva Nose: cilia, mucous to trap bugs Stomach: hydrochloric acid Vagina – lactic acid bacteria prevents growth of other bacteria Called first line of general defence

“We’re in… now what?”

Teacher slide Once a pathogen gets in, what happens then? White blood cells eat them up (phagocytes) Some phagocytes are very big and live a long time looking for pathogens – Macrophages Defence Proteins (Complement) causes pathogens to burst Interferons – prevents viral multiplication

Teacher slide Once a pathogen gets in, what happens then? Inflammation Cells get infected they release chemical call histamine Blood capillaries open wider + become porous Causes swelling, redness heat and pain Inflammation in whole body and inc temp = fever

Human Defence System General Defence System Non-specific Skin, Mucous Membranes & secretions (physical barriers) White blood cells & chemicals to destroy any pathogens that penetrate the body (biochemically inside body)

Human Defence System Specific Defence System (Immune System) Attacks specific pathogens by: Producing Antibodies Killing infected cells

1st line of General Defence System Skin Physical barrier that prevents pathogens getting through Clotting If skin is broken, blood clotting prevents entry of pathogens

1st line of General Defence System Lysozyme Enzyme found in sweat, tears & saliva Attacks & dissolves bacterial cell walls Sebaceous Glands Chemicals that kill bacteria are released in the oil

1st line of General Defence System Mucous Lines many body systems Traps pathogens Acid HCl in stomach kills many pathogens

1st line of General Defence System Cilia Lines respiratory system Beat and move mucous to stomach Coughing helps to move this mucous Beneficial Bacteria Lactic acid Prevents growth of pathogens

Recap Quiz What are Foreign bodies/cells that cause disease ? Pathogens Is the general defence system specific or non-specific? Non-specific What is the first line of defence of the general defence system? Skin, mucous membranes & secretions

Recap Quiz How does the specific defence system work? By producing antibodies & killing infected cells Where would you find lysozyme? Tears, sweat, & saliva What does it do? Dissolve cells walls of bacteria

2nd line of general defence White blood cells Defence Proteins Inflammation

2nd line of general defence WBC Pathogen invades cell Releases chemicals Attracts WBC WBC Phagocytes engulf bacteria

2nd line of general defence

2nd line of general defence Very large phagocytes = Macrophages Long life Some move around body looking for pathogens Some stay in fixed location (e.g. spleen, lymph nodes, tonsils, adenoids, appendix)

2nd line of general defence Defence proteins Complement Interferon (set of 20 proteins) (set of defence proteins)

2nd line of general defence Complement Infection Activates Complement proteins Chain reaction Bursting of viruses & pathogens

2nd line of general defence Interferon Infected body cell Produces interferon Stimulates cells to Prevent viral multiplication Spreads to other cells

2nd line of general defence Infected cell Releases histamine Capillaries dilate Swelling /redness/ heat /pain Fight infection Inflammation WBC

2nd line of general defence Inflammation occurs over whole body Causes increased body temperature Called fever This interferes with the reproduction of viruses and bacteria

Specific Defence System (Immune System) Attacks SPECFIC pathogens Produces Antibodies WBC kill infected cells

Specific Defence System (Immune System) Bone Marrow White blood cells Lymphocytes Monocytes Move to blood vessels Lymph vessels, lymph nodes, Spleen, thymus gland

Monocytes Monocytes Macrophages Digests pathogens Display antigens Antibody production

Macrophages Antigens from pathogen Macrophage

Attack body cells which contain antigens on surface of cell Lymphocytes Attack body cells which contain antigens on surface of cell or Attacks cancer cells Produces ANTIBODIES

Recap What are the components of the 2nd line of general defence? White blood cells Defence Proteins Inflammation

Recap How do the white blood cells work? Attracted by chemicals to the infected cell and engulf bacteria What are the defence proteins? Complement Interferons

Recap What do the complement proteins do? They cause a chain reaction which bursts cells What do the interferons do? They prevent viral multiplication How does inflammation work? Produces heat, swelling, pain and redness and interferes with pathogen reproduction

Recap How does the specific defence system work? It produces antibodies & WBC kill infected cells What are the WBC involved? Lymphocytes & Monocytes

Recap How do the monocytes work? They become macrophages and digest pathogens How do the lymphocytes work? They attack infected cells and they produce antiboides.

Objectives Understand the antigen – antibody response

Antigens Antibody generating Foreign molecule stimulates production of antibodies Teacher notes: Antigens include molecules from the coats of viruses and cell walls of bacteria, fungi and other micro organisms Antigens are also found in parts of foreign cells e.g. pollen grains Does anybody know what happens when the above scenario takes place? Allergic reaction Other places you will find antigens are on incompatible blood transfusions, transplanted organs and cancer cells

Antibody Is a protein produced by white blood cells (called lymphcytes) in response to an antigen

Antibodies Part of family of proteins called IMMUNOGLOBULINS Pathogens can display large number of antigens on its surface Many similar shaped antibodies bind to antigens on surface of pathogen

1. Antibodies attach to antigens Stops pathogen entering new cell 2. Cause pathogens to clump together Allows phagocytes to destroy pathogens 3. Trigger Complement system Pathogenic cells are burst The antigen – antibody reaction is highly specific i.e. there is a precise fit between antibody and antigen Each antigen stimulates the production of only one antibody

How antibodies dispose of antigens Antibodies attach to antigens Stops pathogen entering new cell Cause pathogens to clump together Allows phagocytes to destroy pathogens Trigger Complement system Pathogenic cells are burst

How long does immunity last? 2nd contact – 5 days 1st contact – 14 days Teacher notes: Ask students how long immunity lasts? e.g. if you have the measles as a child and are exposed to them as an adult will you get the measles again? Why? After an infection is overcome, antibody producing lymphocytes stay in the body for a long time. If you are exposed to the same antigen again, the lymphocytes can quickly produce large amount of the specific antibodies So you won’t suffer from the same infection 2nd time round On first contact with a pathogen it takes up to 14 days to produce the max number of antibodies Second time exposed to the same pathogen (antigen) it only takes 5 days to produce antibodies in large numbers

What about colds & flus? Why do we keep getting colds and flus? Many different forms Each have different antigens Mutate constantly

Problems with antigen-antibody reaction Reaction is disabled in people who have AIDS Can produce antibody against own body Allergies Teacher notes: The importance of antibody-allergen reaction is illustrated in people who have AIDS as it is disabled in these people. I.e. they can’t fight infection Sometimes our own bodies produce antibodies against our own tissues e.g. rheumatoid arthritis – joints are attacked or MS where the myelin sheath of nerve cells is attacked Allergies occur when our bodies produce antibodies against materials which should not be antigenic e.g. pollen, food, dust mites etc Therefore allergies are said to be inappropriate immune responses

Recap What is an antigen? Foreign molecule stimulates production of antibodies What is an antibody? Is a protein produced by white blood cells (called lymphcytes) in response to an antigen

Recap What is the name of the family of proteins that antibodies are from? Immunoglobulins How do antibodies dispose of antigens? Antibodies attach to antigens Stops pathogen entering new cell Cause pathogens to clump together Allows phagocytes to destroy pathogens Trigger Complement system Pathogenic cells are burst

Recap How long does immunity last? After an infection is overcome, antibody producing lymphocytes stay in the body for a long time. Name 3 problems associated with antibody-antigen interaction Disabled in AIDS patients Can cause autoimmune disorders (RA & MS) Can cause allergies (inappropriate immune responses)

Induced Immunity Is the ability to resist disease caused by specific pathogens by the production of antibodies 2 types of induced immunity Active Immunity Passive Immunity

Active immunity Production of a person’s own antibodies in response to antigens that enter body Develops after person is infected by virus or bacterium or vaccination Long-lasting as lumphocytes that make the antibody have a long life

Active immunity Natural Artificial Active Active Immunity Immunity Teacher notes: Ask what do you think this means? Natural is the normal way ie we get infected with a pathogen in the normal way and artificial is when we are immunised

Natural Active Immunity Occurs when we get infected in normal way e.g. when we get infected with cold / flu/ chicken pox etc… We develop natural immunity by producing antibodies

Artificial Active Immunity Occurs when we are immunised i.e. get a vaccine A vaccine is a non disease causing dose of a pathogen (or toxin) which triggers the production of antibodies

What is a vaccine? Can contain pathogens that are killed May be only the outer wall / coat of pathogen (this is where the antigens are) Sometimes it is a bacterial toxin Sometimes it is a genetically engineered antigen (no risk of infection)

Develops antibodies to pathogen How does a vaccine work? Receives the vaccine Develops antibodies to pathogen No symptoms infection Life long immunity Notes: The ability to make these antibodies persists in the body conferring life long immunity

History of vaccines Teacher notes: Ask if anyone knows who this is? Edward Jenner The first vaccine was given by EJ in 1796 Jenner had learned that milk maids who had suffered cow pox ( a non fatal viral infection) were resistant to small pox (fatal usually) Jenner inoculated cowpox virus into a young boy. 6 weeks later he inoculated the young boy with small pox Luckily the boy survived Cowpox and smallpox have similar antigens, once the boy had produced antibodies to the cowpox he was immune to smallpox Vacca is the latin for cow and hence Vaccine Smallpox was eradicated in 1976 and now exists only in a laboratory in the USA and Russia

Vaccinations What types can you think of? TB, Diptheria Whooping cough MMR Flu Meningitis

Passive immunity Natural Artificial Passive Passive Immunity Immunity Teacher notes: Ask what do you think this means? Natural passive immunity occurs when a mother passes on immunity either across the placenta or through breast milk artificial Passive immunity is when a person gets an injection of antibodies from another source

Natural Passive Immunity Child gets antibodies from mother Through the placenta Breast milk How long? Only lasts for first few months of life

Artificial Passive Immunity When a person is given an injection containing antibodies from another organism Antibodies act fast to control disease Do not last long – are broken down E.g. anti-tetanus injection Notes: In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus. The horse antibodies are given to an infected person.

Recap What are the 2 types of induced immunity called? Active and Passive What is Active immunity? Antibodies produced in person’s own body 2 types of active immunity what are they? Natural and artificial Notes: In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus. The horse antibodies are given to an infected person.

Recap What is natural active immunity? When pathogens enter the body naturally and you produce antibodies in response What is artificial active immunity? When a pathogen is introduced artificially like vaccine Notes: In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus. The horse antibodies are given to an infected person.

Recap What is Passive immunity? Antibodies from another organism enter a person’s body There are 2 types, what are they? Natural passive immunity Artificial passive immunity Notes: In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus. The horse antibodies are given to an infected person.

Recap What is natural passive immunity? Antibodies enter a body through natural means What are natural means? Breast milk Through the placenta Notes: In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus. The horse antibodies are given to an infected person.

Recap What is natural artificial immunity? Antibodies are injected into a person An example? Anti-tetanus injections Notes: In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus. The horse antibodies are given to an infected person.

Lymphocytes What are lymphocytes? White blood cells Where are they formed? Bone Marrow What is their structure? Large round nucleus and very little cytoplasm

Lymphocytes White blood cells Formed in the Bone Marrow their structure is Large round nucleus and very little cytoplasm 2 types B-lymphocytes – mature in Bone marrow T-lymphocytes – mature in Thymus gland

B-Lymphocytes / B-cells Mature in bone marrow Move to lymphatic tissue especially spleen and lymph nodes Millions of different types of B cells Each B-cell recognises only one antigen & only produces one type of antibody

B-cells B-cell comes into contact with its specific antigen It divides to produce identical B cells These B-cells are called Plasma cells These produce large numbers of the required antibody Plasma cells only live a few days but produce 2000 antibody molecules per second

B - Cells

B-cells How do antibodies inactivate antigens? They attach to them and this allows the cells carrying the antigen to be disposed of by phagocytes or by activating complement (which bursts cells)

B-cells Most die off once the infection has been overcome Some remain alive for years Surviving B-cells allow the body to respond if the same antigen enters the body This secondary response is more effective ? Why

B-cells This secondary response is more effective ? Produces antibodies in response to much smaller amounts of antigen Produces antibodies much faster (5 days as opposed to 14 days) Produces much greater number of antibodies These factors prevent us from being infected more than once by the same pathogen

T-cells Move from bone marrow to thymus where they become activated Important in early months and years of life Do not produce antibodies Act against viruses and bacteria

T-cells 4 types Helper T-cells Killer T-cells Supressor T-cells Memory T-cells

1. Helper T-cells Recognise antigens on surface of other cells Antigens activate helper T-cells T-cells multiply and enlarge and form a group of helper T-cells

1. Helper T-cells Group secretes chemicals e.g. interferons (which prevent viral replication) Chemicals stimulate production & activation of antibody producing B-cells Also stimulates Killer T-cells to reproduce HIV infects helper T-cells (VIDEO)

2. Killer T-cells Attack abnormal body cells i.e. virus infected or cancer cells Stimulated by Helper T-cells Release Perforin Perforin makes pores in the membrane which causes cells to burst Cytotoxic cells

Killer T-cells

3. Suppressor T-cells Growth is stimulate by specific antigens Grow more slowly than other T-cells Become active once pathogen is destroyed Inhibit B-cells and other T-cells Control and stop immune response

4. Memory T-cells Survive for a long time Lifetime Stimulate B-cells to produce antibodies Trigger production of killer T-cells

Recap What are lymphocytes? White blood cells Where are they formed? Bone Marrow What is their structure? Large round nucleus and very little cytoplasm

Recap Where do B-cells mature Bone marrow Where do T-cells mature? Thymus A number of identical B-cells are called? Plasma cells What do they do? Produce antibodies

Recap Describe the secondary response? This secondary response is more effective ? Produces antibodies in response to much smaller amounts of antigen Produces antibodies much faster (5 days as opposed to 14 days) Produces much greater number of antibodies

Recap How many types of t-cells? 4 types Helper T-cells Killer T-cells Supressor T-cells Memory T-cells What does each one do? Helper T – produce chemicals that stimulate b-cells to produce antibodies

Recap Killer T cells? Produce perforin which causes abnormal body cells to burst Suppressor t cells Turn off immune system Memory t cells Survive a long time to trigger immunity to the same antigen later in life.

Recap