Immune System

Immune System

A complex network of cells, tissues, organs, and proteins that protects the body from infection, disease, and other threats

Pathogens

A microorganism that can cause disease

White Blood Cells

• Macrophages

• Neutrophils

• Eosinophils

• Basophils

• Monocytes

• Lymphocytes

  • B 

  • T

First Line of Defense

• Innate Immune Defense

  • Non-specific defense

  • Skin and Mucous membrane

Second Line of Defense

• Non-specific defense

• Macrophages (phagocytic white blood cells)

  • Engulfs and digests pathogens

• Mast cells

  • Assists with allergic and inflammatory responses

  • Contains histamine

Complement System

• Non-specific defense/specific defense

• Works to enhance or complement the action of the immune system

Third Line of Defense

• Adaptive immune defense

• Specific defense

• B and T cells (Lymphocytes)

Adaptive Immunity

A type of immunity that develops when a person’s immune system responds to a foreign substance or microorganism, such as after an infection or vaccination

Antigen

Marker that tells your immune system if something in your body is harmful

Cell mediated Immunity

Cytotoxic T cells

Helper T cells

Cytotoxic T cells

Destroys infected cells by causing apoptosis (self-destruction)

Helper T cells

• Helps activate other white blood cells 

• Also involved in humoral (involves the production of antibodies by B cells)

Cytotoxic Cell Activation

• Process One

  • An infected cell presents an antigen from the pathogen that has infected it. Cytotoxic cells bind and cause apoptosis

• Process Two

  • Macrophages release chemical signals. Helper T cells bind and then release signals. Stimulates cytotoxic T cells

Antibodies

• A blood protein produced in response to and counteracts a specific antigen

  • Found in: mucus, saliva, breast milk, skin, lungs

IgG

• Most abundant type

• Enhances phagocytosis, neutralizes toxins, and triggers the complement system

• Body fluids

IgA

• Mucosal immunity

• Mucus membranes, saliva, tears, and breast milk

IgM

• The first antibody produced in response to infection

• Forming complexes with antigens and activating complement

• Blood and lymph fluid

IgE

• Allergic reactions and parasitic infections

• Lungs, skin, and mucus membranes

IgD

• Lesser-understood antibody role in initiating early immune responses

• Found on the surfaces of immature B lymphocytes

Humoral Immunity

• B cells

• Makes antibodies

Cell-mediated & Humoral Cells

• Helper T cells

  • Helps activate other WBC

• Memory Cells

  • Stores memories of pathogens

  • Memory B Cells

    • Activates Plasma B cells to make antibodies

  • Memory T Cells 

    • Activates cytotoxic T-cells

Active Immunity

• Antibodies produced in response to the presence of a pathogen

• Natural: Direct exposure to disease

• Artificial: vaccine-induced immunity 

• Long-lasting and/or lifelong protection

Passive Immunity

• Given antibodies from another source rather than their own 

• Natural: breast milk, placenta

• Artificial: immunoglobulin, antibody injections

• Immediate protection but temporary