The Human Immune System Video

What is immunity? How our body protects us from pathogens, parasites, and foreign substances. What is a pathogen? Any substance that can cause illness (ex: germs, bacteria, viruses, parasites) Our body has two main types of immunity: 1) Non-specific immunity 2) Specific immunity

1) Non-specific Immunity This is our ability to prevent any bad agent (pathogen) from infecting our body. examples: a) skin b) mucus membranes c) inflammation d) interferons

a) Skin Covers the body so a pathogen can’t get in. Skin is also slightly acidic so bacteria cannot live on it. Upper layer of skin (called the epidermis) is dead and waterproof. Epidermis has the protein Keratin to make it strong (so it doesn’t break open) The dermis (lower skin layer) contains oils & sweat glands. Oil on our skin contains antibodies to kill pathogens.

b) Mucus membranes Nasal passages are lined with hair & mucus to trap pathogens before they get into the lungs Mucus also lines parts of the digestive system and reproductive system in order to prevent pathogens from entering.

c) Inflammation When you get a cut or insect bite, your white blood cells move to the site of injury. These white blood cells prevent the pathogen from getting farther into the body. The heat from the inflammation helps to kill some pathogens and prevents them from spreading.

d) Interferons These are proteins that are secreted by cells once they are infected by a virus. Interferons alert other cells that a virus is in the body. 3 types of interferons: 1) fights viruses 2) fights bacteria 3) another fights various pathogens

2) Specific Defenses These include cells in our body that fight specific pathogens in the body. (They work together to kill almost any invader) There are two types of specific immunity: a) Humoral immunity (B-cells) b) Cell-mediated immunity (T-cells) Video

a) Humoral immunity B-cells (or B Lymphocytes) make antibodies to ciruculate in the blood and lymph (lymph glands). When a pathogen enters the body, our B-cells recognize what kind of pathogen it is. For EVERY pathogen there is ONE type of antibody that fights it. Video

a) Humoral immunity cont… B-cells DO NOT destroy cells. They do 2 things: 1) make the toxin released from the pathogen less dangerous (so we don’t get as sick) 2) clump many pathogen cells together so they are easier to destroy

b) Cell-mediated immunity T-cells destroy pathogens in our body. (2 types of T-cells) 1) Cytotoxic T-cells Kill cells that have released interferon (or cells that are infected) 2) Helper T-cells Help identify infected cells so cytotoxic t-cells know what to “target”

What is 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 – You fought it, you won, you remember it Planned exposure to a form of the antigen that has been killed or weakened – You detected it, eliminated it, and remember it What is this second type of exposure called?

Vaccine Antigens are deliberately introduced into the immune system to produce immunity Because the bacteria has been killed or weakened, minimal symptoms occur 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

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 came out to be about 100 million people

Do we get all the possible vaccines we can? Although the Center for Disease Control (CDC) recommends certain vaccines, many individuals go without them Those especially susceptible include travelers and students Consider the vaccine for meningitis, which is recommended for all college students and infects 3,000 people in the U.S., killing 300 annually Link

Passive Immunity You don’t produce the antibodies A mother will pass immunities on to her baby during pregnancy These antibodies will protect the baby for a short period of time following birth while its immune system develops. Lasts until antibodies die Thymus Placenta

Immune Disorders ~Allergies~ Immune system mistakenly recognizes harmless foreign particles as serious threats Launches immune response, which causes sneezing, runny nose, and watery eyes Anti-histamines block effect of histamines and bring relief to allergy sufferers

Aquired Immune Deficiency Syndrome Caused by the Human Immunodeficiency Virus Discovered in 1983 Specifically targets and kills T- cells Because normal body cells are unaffected, immune response is not launched

AIDS ~The Modern Plague~ The HIV virus doesn’t kill you – it cripples your immune system With your immune system shut down, common diseases that your immune system normally could defeat become life- threatening Can show no effects for several months all the way up to 10 years

AIDS ~The Silent Spread~ Transmitted by sexual contact, blood transfusions, contaminated needles As of 2007, it affects an estimated 33.2 million people