Immune System BiologyMarch 2014 Ms. Boehm

What is the Immune System? The body’s defense system, which fights off pathogens that cause disease- it keeps you healthy! Pathogen = a foreign substance that can cause disease Bacteria, virus, etc.

1 st Line of Defense All first line of defense is non-specific, meaning they don’t distinguish among pathogens Skin: shields body from harmful invaders (Barrier)

1 st Line of Defense Mucus & Cilia: (Barriers) Mucus traps foreign microbes & dust that are allowed in through nasal hair hair-like structures (cilia) in the lungs sweep mucus upward & out of system

1 st Line of Defense What’s the first thing you do when you cut your finger? Saliva: contains chemicals that break down bacteria (Barrier)

1 st Line of Defense Stomach Acid: swallowed bacteria is broken down by strong acids in stomach (Barrier)

2 nd Line of Defense The second line of defense is non-specific as well, but is now inside the body/bloodstream White Blood Cells: if invaders do make it inside the body, WBC’s engulf & destroy them Also known as phagocytes or leukocytes Perform phagocytosis- cell eating Breakdown of bacteria occurs in lysosome Video

2 nd Line of Defense Another 2 nd line of defense is the inflammatory response The chemical response is known as histamines you have probably taken an antihistamine before

3 rd Line of Defense The third line of defense is a specific, targeted attack on pathogens Able to distinguish self vs. non-self invaders Has a role in immunity Each antibody is specific to a certain antigen

Types of WBC’s Lymphocytes = originate in the bone marrow & travel throughout lymphatic system to recognize specific invaders B cells = programmed to make certain antibodies Develop in bone marrow T cells = responsible for attacking & destroying harmful pathogens Develop in thymus gland

How do Antigens work? Antigens are proteins on the outside of a pathogen, unique to each one identifies the pathogen as non-self and the body uses it for identification and marks it for destruction Immune system responds by releasing Antibodies, which fit onto the Antigens perfectly Antibodies: proteins that attach to specific antigens in the body (made by WBC’s) antigen pathogen antibody

What happens next? Once the Antibodies are attached to the antigen, it triggers a macrophage to come along and engulf the entire pathogen antigen pathogen antibody macrophage (WBC)

Stop and Review What is the role of the immune system? Compare and contrast the 1 st, 2 nd and 3 rd lines of defense. How are they similar, how are they different? Define antigen and antibody. Relate the two terms to each other. What type of organelle do you think a macrophage must have a lot of?

Immunity Why is it impossible to get the same type of cold twice? Your body has been exposed to the antigen You make antibodies that eventually destroy it The next time that same antigen tries to come around, those same antibodies will destroy it immediately

Immunity How do Vaccines work? Your body is injected with dead or weakened version of the ________________.

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 A form of H1N1 that is present again today. It infected 20% of the human population and killed 5%, which came out to be about 100 million people

Immune Disorders Allergies When your immune system mistakes harmless foreign particles (dust, pollen) as serious threats Immune system launches a response, which causes sneezing, runny nose, & watery eyes

Immune Disorders Autoimmune diseases The immune system turns against itself The surface proteins on our own cells are viewed as foreign and the body makes antibodies to destroy the cells Not sure why the body turns against itself Examples: Rheumatoid arthritis, lupus, type I diabetes

Immune Disorders Acquired Immune Deficiency – AIDS Caused by Human Immunodeficiency Virus (HIV) Discovered in 1983 Targets and kills T-cells Immune System is weakened HIV doesn’t kill you Common diseases that your body can no longer fight off can become life-threatening

Immune Disorders Acquired Immune Deficiency – AIDS Transmitted through sexual contact, blood transfusions, contaminated needles AIDS affects over 40 million people worldwidepeople