The Immune System Chapter 24

What you need to know! Several elements of an innate immune response The differences between B and T cells relative to their activation and actions. How antigens are recognized by immune system cells. The differences in humoral and cell-mediated immunity. Why Helper T cells are central to immune responses.

Immune System Function: fight infection using cells to destroy invading substances Two divisions: Nonspecific (innate immunity) Specific

Nonspecific (Innate immunity) Nonspecific = doesn’t matter which disease you have First line of defense Second line of defense Interferon

First Line of Defense Prevent the enemy from breaching the perimeter Skin, mucus, cilia are tools your body uses to deny the enemy access to your body

Second Line of Defense Should the enemy breach the perimeter a second line of defense is necessary Inflammatory response White blood cells move into the damaged area surround and destroy the invaders Fever Histamine released by damaged tissue trigger a rise in body temperature Cooks invaders Raises heart rate

Inflammatory Response Wound Skin Phagocytes move into the area and engulf the bacteria and cell debris Bacteria enter the wound Capillary

Animations http://www.youtube.com/watch?v=CmbWE3jLUgM http://www.youtube.com/watch?v=uNG-jZxvhcg

Interferon Proteins that “interfere” with viral reproduction Infected cells release interferons to help healthy cells prevent viral reproduction

Lymphatic System Works with the immune system to clean blood and make white blood cells Consists of nodes the thymus and bone marrow

End Part I

Specific Immune System Strategies the body uses to defeat a particular disease (acquired immunity): B cell humoral immunity T cell-mediated immunity

Acquired Immunity Triggered by a foreign molecule (antigen) Immune response to antigens is either: More white blood cells, or Antibodies An antibody is a protein in blood that attaches to a specific antigen

Immunity Resistance to specific invaders Active immunity: your immune system makes the antibodies learned by natural exposure or vaccination Passive immunity: receive premade antibodies Fetus from mother’s blood Baby from mother’s milk antivenin

Lymphocytes White blood cells usually found in the lymphatic system Specialize into B or T cells depending on where they mature B cells = bone marrow T cells = thymus Both cells use antigen receptors in their membranes to detect invaders

Humoral Immunity Antigen binds to a B cell’s antigen receptor B cells divide rapidly into two new cells Plasma cells Make antibodies Memory B cells Remember the invader for next time Antibodies attach to the invaders to disrupt function or to target them for macrophages

Humoral Immunity

Cell-Mediated Immunity T Cells kick-in when antigens are embedded in our own cells (cancerous or infected) Macrophages identify antigens and embed them in their membrane Helper T cells identify the antigen and stimulate cytotoxic cells to annihilate any cell with the specific antigen Cytotoxic cells (killer T cells) stimulate the targeted cell to kill itself (apoptosis)

Cell Mediated Activity Helper T cell activates killer T cells and B cells Macrophage T cell binds to activated macrophage Helper T Cell Killer T Cell T Cell T cell, activated by macrophage, becomes a helper T cell Antigens are displayed on surface of macrophage Infected Cell Killer T cells bind to infected cells, disrupting their cell membranes and destroying them

Animations http://www.youtube.com/watch?v=1tBOmG0QMbA