The Immune System Nonspecific and Specific Defense You do not need to write down anything in blue.

What is a pathogen? Pathogen: disease causing agent Pathogen: disease causing agent Harmful to living thingsHarmful to living things Check out this slow motion sneeze! GVMlns4

Examples of Pathogens include Bacteria Bacteria Viruses Viruses Parasites, like fungi, protists, & worms Parasites, like fungi, protists, & worms

SoilSoil WaterWater Infected animalsInfected animals FoodFood Animal BitesAnimal Bites –This includes mosquitoes (West Nile Virus), ticks (Lyme Disease), fleas (Bubonic plague), flies (various infections) Person-to-person contactPerson-to-person contact How are Pathogens Spread?

Q: How do bacteria cause damage to host cells? A: By releasing poisonous substances called toxins. Did you know?…the Tetanus bacteria is found in soil and one drop of the toxin, the size of a period, can kill 30 people. These images are of two men undergoing an extreme muscle spasm caused by toxins produced by tetanus bacteria.

The Immune System  Immune System: body system that fights off invading pathogens  Two types of defense: Nonspecific DefenseNonspecific Defense Specific DefenseSpecific Defense

1 st line of Non-Specific Defense b A physical barrier to pathogens. b Skin: A physical barrier to pathogens. Any break in the skin allows entry.Any break in the skin allows entry. Releases sweat, oils, and waxes that contain chemicals toxic to bacteria.Releases sweat, oils, and waxes that contain chemicals toxic to bacteria. b Tissues that line internal body surfaces that are in contact with the environment. b Mucous membranes: Tissues that line internal body surfaces that are in contact with the environment. Sticky fluid that traps pathogens.Mucous: Sticky fluid that traps pathogens.

1 st line of Defense: Types of Non-specific Defense b Has acid that destroys potential pathogens that are swallowed b Stomach: Has acid that destroys potential pathogens that are swallowed b WBC’s that ingest (eat) pathogens b Phagocytes: WBC’s that ingest (eat) pathogens Ingest and destroy pathogens.Macrophages: Ingest and destroy pathogens. Ingest pathogens, then secrete deadly toxic chemicals to kill themNeutrophils: Ingest pathogens, then secrete deadly toxic chemicals to kill them Short video clip on phagocytes: video clip on phagocytes: Phagocytes and their relatives

Macrophage Neutrophils

1 st line of Defense: Types of Non-specific Defense b b Moderate Fevers (< 103 O F): Inhibit growth of pathogens and recruit macrophages b b Inflammation: Reaction to tissue damage. Phagocytes consume foreign substances. (Symptoms: swollen, redness, heat, pain)

Inflammation Figure 24.2 Tissue injury; release of chemical signals such as histamine. 123 Dilation and increased leakiness of local blood vessels; migration of phagocytes to the area. Phagocytes (macrophages and neutrophils) consume bacteria and cell debris; tissue heals. Pin Skin surface Bacteria Chemical signals WBC Swelling Phagocytes and fluid move into area Phagocytes

Specific Defense: The Immune System   Organs of the Immune System : Bone Marrow: makes WBC Thymus gland: where T cells mature Lymph nodes: contain lots of WBC Spleen: removes pathogens from blood

The Immune System involves many types of White Blood Cells (aka Leukocytes / WBCs). Here are a few types: B lymphocytes: Secrete antibodies. Antibodies: Y-shaped molecules that grab and block certain pathogens. T lymphocytes: Help stimulate an immune response. You can call them B cells and T cells for short!

Specific Defense: Recognizing Pathogens bbIbbImmune Response: your wbcs attack something bbAbbAntigen: anything that causes a response Recognition: –L–L–L–Lymphocytes have receptor proteins all over them. –R–R–R–Receptor proteins recognize and bind to antigens that match the receptor.

Immune Response gets stronger over time b b Primary Immune Response: 1 st time a certain pathogen is encountered by the body After infection is fought, some B and T cells stay alive for years as memory cells. Memory cells can divide to fight pathogens that they “remember” if they ever meet again.

b b Secondary Immune Response: a later exposure to the same pathogen Response is faster and stronger due to memory cells. Draw this graph!