The immune system
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THE IMMUNE SYSTEM. Immunity. Immunity The ability of the body to fight infection and/or foreign invaders by producing antibodies or killing infected cells. Immune System

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  • Immunity

    • The ability of the body to fight infection and/or foreign invaders by producing antibodies or killing infected cells.

  • Immune System

    • The system in the body responsible for maintaining homeostasis by recognizing harmful from non-harmful organisms and produces an appropriate response.

Foreign invaders
Foreign Invaders

  • Called Pathogens

    • Viruses, bacteria or other living thing that causes disease or an immune response.

  • Antigens

    • Toxins that pathogens produce that cause harm to an organism. (Anything identified as non-self)

Parts of the immune system
Parts of the Immune System

  • Blood - White Blood Cells in particular.

  • Lymph nodes

  • Thymus Gland – Produces T Lymphocytes

  • Bone Marrow – Produces B Lymphocytes

The body s lines of defense
The Body’s Lines of Defense

First Line of Defense – The Skin

  • Provides Physical and Chemical barriers

    • Physical – hard to penetrate, made of indigestible keratin

    • Chemical – tears, sweat

Nonspecific immune response
Nonspecific Immune Response

Second Line of Defense - These are defenses the body uses no matter what the invader may be. These defenses include:

  • Phagocytosis –done by macrophages

  • Natural Cell Killers

  • Inflammation - caused by release of Histamine from leukocytes

  • Fever – caused by histamines. The fever (high temp) kills invaders by denaturing their proteins.

Specific immune response
Specific Immune Response

Third Line of Defense – This is a specific response to a specific pathogen/antigen.

  • The response involves the creation of antibodies.

Cells of the immune system
Cells of the Immune System

White Blood Cells

  • Phagocytes - Neutrophils

    - Macrophages

  • Lymphocytes


  • 60% of WBCs

  • ‘Patrol tissues’ as they squeeze out of the capillaries.

  • Large numbers are released during infections

  • Short lived – die after digesting bacteria

  • Dead neutrophils make up a large proportion of puss.


  • Larger than neutrophils.

  • Found in the organs, not the blood.

  • Made in bone marrow as monocytes, called macrophages once they reach organs.

  • Long lived

  • Initiate immune responses as they display antigens from the pathogens to the lymphocytes.

The immune response explained
The Immune Response Explained

  • Antigen infects cells.

  • Macrophageingests antigen and displays portion on its surface.

  • Helper T- Cell recognizes antigens on the surface of the macrophage and becomes active.

  • Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells.

  • Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells.

The immune response explained1
The Immune Response Explained

6. Active Cytotoxic T-Cells kill infected cells.

7. At the same time, B-Cells divide into Plasma Cells and Memory B- Cells.

8. Plasma cells produce antibodies that deactivate pathogens.

9. Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.

10.Supressor T-Cells stop the immune response when all antigens have been destroyed.

Active and passive immunity
Active and Passive Immunity

Active immunity

  • Lymphocytes are activated by antigens on the surface of pathogens

  • Natural active immunity - acquired due to infection

  • Artificial active immunity – vaccination

  • Takes time for enough B and T cells to be produced to mount an effective response.

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Active and Passive Immunity

Passive immunity

  • B and T cells are not activated and plasma cells have not produced antibodies.

  • The antigen doesn’t have to be encountered for the body to make the antibodies.

  • Antibodies appear immediately in blood but protection is only temporary.

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Active and Passive Immunity

Artificial passive immunity

  • Used when a very rapid immune response is needed e.g. after infection with tetanus.

  • Human antibodies are injected. In the case of tetanus these are antitoxin antibodies.

  • Antibodies come from blood donors who have recently had the tetanus vaccination.

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Active and Passive Immunity

Natural passive immunity

  • A mother’s antibodies pass across the placenta to the fetus and remain for several months.

  • Colostrum (the first breast milk) contains lots of IgA which remain on surface of the baby’s gut wall and passes into blood.

Autoimmune diseases
Autoimmune Diseases

  • Autoimmune diseases are diseases where the immune system begins to attack itself.

    • Ex:

      • Rheumatoid Arthritis – crippling disease of the joints.

      • Lupus – disease of blood and organs.

      • Multiple Sclerosis – disease of nervous system

  • Cause(s): unknown

  • Cures/Treatments: No known cures. Usually treated with drugs.