The Human Immune System

When the Castle is Under Attack The Immune System Responds!

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

Organs/Tissues/Cells of the Immune System Spleen Thymus Bone Marrow Tonsils Lymph Nodes Lymphocytes

Disease Any change (other than injury) that disrupts the normal function of the body Pathogen is a disease-causing agent Can be bacteria, viruses, fungi, protists, worms

Do not write, just listen Pathogen - Virus Insert their RNA or DNA into host cells Can infect plants, animals, and bacteria Small Pox Warts Do not write, just listen Bacteriophage

Do not write, just listen Pathogen - Bacteria Can break down tissues or release toxins that harm the body clostridium botulinum Botulism Do not write, just listen

Do not write, just listen Pathogen - Fungus Fungi penetrate the outer layers of skin Can infect the mouth, throat, nails Do not write, just listen

How Are Diseases Spread? Infected animals Physical Contact Contaminated Food and Drink

How does the body defend against disease? (Innate) 1st Line of Defense - Prevent Entry (Innate) 2nd Line of Defense - Search and destroy (Acquired) 3rd Line of Defense - Immunity

Non-Specific vs Specific Defenses Non-specific defenses do not discriminate between one threat and another Specific defenses have “memory” of the pathogen and gives us immunity to certain diseases

First Line of Defense Prevent Entry

1st Line of Defense (Non-specific) Skin - Fortress or Gate In order for a pathogen to invade our body, it must first breach our skin.

Skin Epidermis - outer layer of skin. Constantly sloughs off and prevents bacteria from colonizing Sweat and oils contain anti-microbial chemicals

1st Line of Defense (Non-specific) Mucus & Cilia Mucus contains enzymes that destroy bacterial cell walls Cilia moves mucus with trapped pathogens out of body

1st Line of Defense (Non-specific) Saliva Saliva contains chemicals that break down and destroy pathogens

1st Line of Defense (Non-specific) Stomach Acid Stomach Acid breaks down swallowed pathogens The stomach is lined with a special mucus to prevent damage

Stop Here

Second Line of Defense Search and Destroy

2nd Line of Defense (Non-specific) WBC - Phagocyte/Macrophage “The Guards” These white blood cells surround and engulf germs that have recently entered the body. Phagein - to eat or devour

Virus Attack! Viruses turn cells into virus-making factories. The cell will eventually burst and release thousands of viruses that will infect new cells. Cell before viral infection Cell after viral infection

How do cells defend against viruses? Interferon!

2nd Line of Defense (Non-specific) Interferon Virus-infected cells release interferon when an invasion occurs Interferon is a chemical that interferes with viral replication

What happens to already infected cells? Fever Inflammatory Response T Cells

2nd Line of Defense (Non-specific) Fever Increased body temp leads to increased heart rate. More white blood cells get to site of infection Pathogens can only survive in a narrow temperature range

2nd Line of Defense (Non-specific) Inflammatory Response Capillaries dilate to increase blood flow, WBC move to infected area Redness, swelling and pain Increased temperature

2nd Line of Defense (Non-specific) Killer T-Cells Recognize and attack infected cells and cancer cells Quickly kill infected cells and search for more cells to kill

Stop Here

Third Line of Defense Immune Response (Specific Defense)

Immune Response (Specific Defense) A series of specific defenses that attack a particular disease-causing agent is called an Immune Response