Immune System Immune System 3 lines of defense

Immune System

Immune System 3 lines of defense: • First line – Barriers –Ex: Skin, saliva, tears • Second line – Internal non specific –Ex: Phagocyte (cell eater), antimicrobial proteins, inflammatory response • Third line – Targeted (specific) –Ex: B cells, T cells, memory cells, antibodies

Immune System Non Specific Response = 1 st and 2 nd line of defense - same regardless of pathogen Specific Response = 3 rd line – very specific, targeted to the pathogen

First Line of Defense External • Skin: Constantly shedding, outer layer = tough dead cells (hard to get through) • Sweat and oil glands: secrete oils and acids that prevent growth of colonies • Saliva, tears: contain lysozome, an enzyme that breaks down bacterial cell walls

Second Line of Defense Internal • Antimicrobial Proteins – Prevent bacteria from reproducing • Phagocytes – White blood cells that engulf (eat) invaders • Inflammatory Response – Delivers proteins and phagocytes GENERAL, NONSPECIFIC! (WORKS ON A WIDE RANGE OF PATHOGENS)

• Inflammatory response: – Occurs with injury to a tissue – Response to chemical signals (histamines) – More blood flows to area, resulting in redness, swelling, sometimes fever – Delivers antimicrobial proteins and phagocytes

Third Line of Defense B Cells and T Cells Types of white blood cells crucial for the immune response They have receptors that recognize the antigen, a structure that triggers the immune response (often found on pathogens).

B and T cells • When they recognize the pathogen, they bind to it, then reproduce. When they reproduce, they create: – Effector / Plasma Cells Fighter cells that attack the pathogen – Memory cells launch quicker immune attack in the future B Cells Make antibodies that can bind to pathogen and prevent it from entering and infecting cells, or can bind to pathogen and flag it for phagocytosis T Cells Helper T Cells activate B and T cells to reproduce/attack. Killer T Cells destroy body cells that have been infected by a pathogen

Antibodies – Made by B Cells – Are specific to certain pathogens (fit like a key in a lock) – Can work by: 1. Sticking to pathogen and preventing it from infecting cells 2. Flagging pathogen for WBC to kill them 3. Working with proteins to destroy the germ

How do vaccines work? (add this info in a margin) • Vaccines give your body a dose of the pathogen • Your immune system launches an attack by making antibodies and memory cells