Nonspecific Defenses October 20, 2008

Review What is a pathogen? Pathogen is any agent that causes diseases “PATHO” means diseases Examples: 1. Virus – HIV, cold, flu 2. Bacteria – pneumonia, tuberculosis, meningitis 3. Protists – Malaria, Lyme diseases Plasmodium-malaria causing bacteria found in mosquito HIV infecting a cell

Immune System The Immune system is the body’s main defense against pathogens. The immune system recognizes, attacks, destroys, and remembers each type of pathogen that enters the body. Immunity- the process of the immune system fighting infection

Immune System 1. Nonspecific defenses 2. Specific defenses The immune system has two categories of defense mechanisms against infection: 1. Nonspecific defenses Like fortress walls Guard against infection by keeping most of things out of the body 2. Specific defenses Like security guards Track down harmful pathogens that managed to break through the body’s nonspecific defenses

Nonspecific Defenses NONSPECIFIC defenses do not discriminate between one threat and another. 1. First line of defense: SKIN Function- to keep pathogens out of the body Skin works as a barrier against infection Most pathogens cannot penetrate through the skin’s surface SECTRETIONS FROM THE BODY The body secretes mucus, saliva, and tears which all contain lysosomes to break down the cell walls of bacteria, and oil and sweat which produce an acidic environment.

Nonspecific Defenses 2. Second line of defense: INFLAMMATORY RESPONSE A non-specific defense reaction to tissue damage caused by injury (broken/sprained bone, bump on the head) or infection (infected cut or scrape). FEVER When your body releases chemicals that increase the body’s core temperature and speed up your heart rate. Increased body temperature is advantageous because many pathogens can not survive at high temperatures, and increased heart rate helps white blood cells get to the site of infection faster. 6

Nonspecific Defenses Inflammatory response 7

SKIN “Good fences make good neighbors” The largest organ of the body – a covering over the entire body. Epidermis – the outer layer of the skin Outside of epidermis is made up of dead cells Inner layer is made up of living cells Dermis – the inner layer of the skin Under the epidermis Contains blood vessels, nerve endings, sensory receptors, hair follicles, sweat glands, etc.

Reflection (Answer all questions in complete sentences) What are the four “jobs” of your body’s immune system? Use an analogy to explain the two different levels of your immune system. What is your body’s main defense against pathogens? What is one response that your second line of defense has towards infection or injury.

Specific Defenses If a pathogen is able to get past the body’s nonspecific defenses, the immune system reacts with specific defenses Specific defenses that attack the particular pathogen (disease-causing agent) are called immune responses This is triggered by antigen What is an antigen? Anything that triggers immune response – like an ID card of pathogens (ex: virus, bacteria, other pathogens) Each pathogen has its own antigen 10

Humoral Immunity B Cells Plasma cells When a pathogen invades the body, B cells recognize its antigen (“uh oh”) B cells then grow and divide (reproduce) rapidly Some B cells grow and become plasma cells Some B cells grow and become memory B cells Plasma cells Plasma cells immediately respond to the infection by releasing antibodies 11

Antibodies What are Antibodies? Antibodies are proteins that recognize and bind to antigens (of pathogens) What do antibodies do? Antibodies are carried in the bloodstream to attack the pathogen (what is causing the infection). Antibodies overcome the infection in one of two ways: They kill the antigen directly. They signal other immune cells (like white blood cells and macrophages) that antigens are present in the body. 12

Antibodies 13

Humoral Immunity Memory B cells Long term immunity Once the body has been exposed to a pathogen, many memory B cells remain capable of producing antibodies specific to that antigen The reaction to a second infection by the same pathogen is much faster 14