The Human Immune System

Did you know? In the mid-1300’s, 25 million people died from the plague which was caused by a bacterial pathogen carried by the fleas on rats. Around 1850, a British surgeon named Joseph Lister, wondered if pathogens were being transferred from surgeons hands and medical equipment to patients. After surgeons started to clean their hands, scalpels etc. the death rate fell significantly!

Four Ways to Transmit Infectious Diseases DIRECT Contact Shaking hands Sharing Drinks/Food Sharing Bodily Fluids INDIRECT Contact Being near an infected person Sneezing Coughing *Some pathogens can travel up to 5m* WATER & FOOD Eating infected foods E. coli Salmonella Coliform ANIMAL BITES Bitten by an animal carrying the rabies virus

What is the IMMUNE system? The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles.

Your immune system has powerful defences to fight pathogens that are constantly attacking your body….. *THE FIRST LINE OF DEFENCE* *THE SECOND LINE OF DEFENCE*

The First Line of Defence ~Skin~ The dead, outer layer of skin, known as the epidermis, forms a shield against invaders. Dead skin cells are constantly sloughed off, making it hard for invading bacteria to colonize. Sweat and oils contain anti-microbial chemicals, including some antibiotics. You shed between 40 – 50 thousand skin cells every day!

The First Line of Defence ~Mucus and Cilia~ As you breathe in, foreign particles and bacteria bump into mucus throughout your respiratory system and become stuck. Mucus contains lysozymes, enzymes that destroy bacterial cell walls. The normal flow of mucus washes bacteria and viruses off of mucus membranes. Hair-like structures called cilia sweep this mucus into the throat for coughing or swallowing. Cilia in the respiratory tract move mucus out of the lungs to keep bacteria and viruses out.

The First Line of Defence ~Saliva and Tears~ Saliva and tears contain many chemicals and enzymes that break down bacteria. However, there are thousands of different types of bacteria can survive these chemicals.

The First Line of Defence ~Stomach Acid~ Swallowed bacteria and pathogens are broken down by an incredibly strong acidic gastric juice that is secreted by the lining of the stomach. The stomach must produce a coating of special mucus or this acid would eat through the stomach!

The Second Line of Defence If a pathogen makes it past the first line of defence then your body launches an attack against the pathogen. Your body needs to be able to distinguish between invading cells and cells that belong. Once it realizes the unknown cell is an invader, it will launch the attack.

The Second Line of Defence There are two types of immune responses. *INNATE Immune Response -a response we are born with *ACQUIRED Immune Response -a highly specific response our bodies must build

The Second Line of Defence Innate Immune Response ~Inflammation~ The first action of the Innate Immune Response is the flow of FLUID, CELLS and dissolved substances from the BLOOD to the site of infection. This causes fever, swelling and redness – which is known as INFLAMMATION. White blood cells, called PHAGOCYTES, increase. Their job is to search for invading pathogens and destroy them. Video

The Second Line of Defence Innate Immune Response ~Phagocytes~ These white blood cells are responsible for eating foreign particles by engulfing them. Once engulfed, the phagocyte breaks the foreign particles apart in organelles called Lysosomes. In Greek, phago means to eat, and cyte means cell.

The Second Line of Defence Acquired Immune Response This is a highly specific attack on a pathogen or antigen. PATHOGEN: Disease causing organism or substance. ANTIGEN: Any substance the body cannot recognize, from a virus to a splinter.

The Second Line of Defence Acquired Immune Response Disposal Mobilization Recognition Immunity B Cell White Blood Cell Nucleus Helper T Cell Memory B Cell Antibody Pathogen

The Second Line of Defence Acquired Immune Response Recognition White blood cells surround the pathogen and signal T Cells. More T Cells are produced. Then the Helper T Cells signal the B Cells. Mobilization B Cells produce antibodies. Disposal Antibodies destroy pathogens and antigens. Immunity Some antibodies (Memory B Cells) remain for future use. This is called “Active Immunity”.

The Second Line of Defence Acquired Immune Response This response can take up to a week to develop, because your body needs time to develop the exact response needed to defeat the particular invader. Another type of T Cell is called a ‘Killer T Cell’. Killer T Cells can work independently and directly destroy antigens or pathogens. They also destroy cancer cells.

Cell before infection… Viruses Viruses are non-living particles that enter body cells, hijack their organelles, and turn the cell into a virus making-factory. The cell will eventually burst, releasing thousands of viruses to infect new cells. If you have ever heard of HIV, chicken pox, cold sores or the flu – then you have heard of viruses. *A virus will insert its DNA into the nucleus of the host cell and ‘trick’ the cell into making new virus particles. Cell before infection… …and after.

What is Immunity? Active Immunity Passive Immunity Resistance to a disease causing organism or harmful substance. Two types Active Immunity Passive Immunity

Active Immunity You produce the antibodies Your body has been exposed to the antigen in the past either through: Exposure to the actual disease causing antigen – Your immune system fought it, won, and Memory B Cells remain. Planned exposure to a form of the antigen that has been killed or weakened – Your immune system detected it, eliminated it, and remembered it.

Vaccines Antigens are deliberately introduced into the immune system to produce immunity. This is done through immunizations when you are a baby, through to adulthood. The vaccine is a weakened form of the disease. It stimulates the immune system to create antibodies against the disease. The antibodies are then reactivated if ever the disease enters your body again. Vaccines have eradicated or severely limited several diseases from the face of the Earth, such as polio and smallpox.

How long does active immunity last? It depends on the antigen. Some disease-causing bacteria multiply into new forms that our body doesn’t recognize, requiring annual vaccinations, like the flu shot. Booster shot - reminds the immune system of the antigen. Others last for a lifetime, such as chicken pox.

Passive Immunity You don’t produce the antibodies A mother will pass immunity onto her baby during pregnancy through the placenta. These antibodies will protect the baby for a short period of time following birth while the baby’s immune system develops. The immunity will last until the antibodies die.

Think the flu is no big deal? Think again… In 1918, a particularly deadly strain of flu, called the Spanish Influenza, spread across the globe. It infected 20% of the human population and killed 5%, which was about 100 million people.

Immune Disorders ~Allergies~ An allergy is an unusually high sensitivity to some substance. If this substance causes an allergic reaction, it is known as an allergen. * Examples of allergens are: foods, pollen, dust and animals. Symptoms of allergies include sneezing, runny nose, watery eyes, rash, and swelling. These symptoms result from a side effect of a substance called histamine. Anti-histamines block the effect of histamines and bring relief to allergy sufferers. They do not cure the allergy, they just reduce the symptoms.

Immune Disorders ~Allergies~ Some people are highly allergic to allergens (such as bee stings or peanuts). Exposure to these allergens can trigger anaphylactic shock which can result in swelling, difficulty breathing, and sometimes death. For this reason, people with these allergies must carry an Epipen with them.

Immune Disorders ~ Acquired Immune Deficiency Syndrome (AIDS) Caused by the Human Immunodeficiency Virus (HIV). Discovered in 1983. It is a powerful pathogen that attacks the immune system and specifically targets and kills Helper T-cells. This means that when other pathogens enter the body, the immune system is unable to activate Killer T cells or B cells. A person infected with HIV can die from other infections as a result from their weakened immune system. HIV is transmitted through: -body fluids -semen -blood -unprotected sex -sharing needles -blood transfusions

Taking Care of Your Immune System Eat a well balanced diet. Maintain your personal hygiene (brush your teeth, bathe, wash your hands often). Keep your home clean. Get plenty of rest and exercise. Keep your vaccinations up to date. Avoid tobacco and other non-prescription drugs. Do not engage in activities that involve sharing bodily fluids with others. http://www.brainpop.com/health/bodysystems/immunesystem/preview.weml