The Immune SystemPacket #22

Chapter #31

Introduction

The immune system includes all of the structures and processes that provide a defense against potential pathogens (disease causing agents).

Immunity, the ability of an organism to resist disease, are in two forms Passive Immunity

Immunity passed from mother to child

Via genes There is no immune response

Active Immunity The body produces a response to

a particular pathogen.

Active ImmunityHuman Body Defense Mechanisms

Human Body Defense Systems

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Defense Mechanisms Non-Specific

Defense is a rapid response to a wide range of pathogens

Specific Takes several days to mount Delivered by the Immune

System Lymphocytes

Lymphocytes

Introduction

Lymphocytes (a type of white blood cell) are derived from unspecialized stem cells in the bone marrow.

Large numbers of lymphocytes are found in the thymus, spleen and lymph nodes.

There are two types of lymphocytes T cells

Thymus-dependent lymphocytes

B cells Derived from the discovery of B

cells in the bursa of Fabricius Mammals do not have this

organ

B Cells

Secrete antibodies (proteins) into the blood and lymph in order to inactivate pathogens.

Combat bacterial infections and some viral infections Because blood and lymph

are body fluids (humors), and since they release antibodies, the B cells are said to provide humeral immunity (antibody-mediated immunity)

T Cells

Attack host cells that have become infected with viruses or fungi, transplanted human cells and/or cancerous cells.

These cells do not secrete antibodies.

Must be in close proximity to destroy the infected cell.

Provide cell-mediated immunity. Cell-mediated immunity

involves the use of T cells.

Humoral Immuntiy vs. Cell-Mediated Immunity

See Pages 764 & 765 in textbook.

Specific Mechanisms

Specific Defense Mechanisms

Antigens Molecules (proteins), found on

the surface of cells, that stimulate the production of specific antibodies. The ID card. Natural Foreign

Haptens Small organic molecules that

can become antigens if they are bond to proteins.

Immunoassays*

Non-Specific Mechanisms/Barriers

Non-Specific Defense Mechanisms

Phagocytosis Engulfing of pathogens

Neutrophils Macrophages Phagocytes

Fever Produced by cytokines High fevers are dangerous

however fevers aid in the destruction of pathogens

Interferons Polypeptides that act as

messengers that protect other cells in the vicinity from viral infection.

The non-specific defense systems utilizes different “defensive lines” in order to be successful. {*Similar to having an alarm system for the house but

there are specific sensors, at the doors and windows for example, that trigger the alarm system.}

Introduction

The Immune SystemNon-Specific Defense System

Barriers/MechanismsThe First Line of Defense

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The Skin Mucous Membranes Cilia

Lines the lungs

Gastric Juice In the stomach Kills most microbes

The Immune SystemNon-Specific Defense Barriers/Mechanisms

The Second Line of Defense

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Second Line of Defense Inflammatory Response

Redness; swelling; heat; pain

Lymphocytes are activated.

Fever is developed.

The Immune SystemNon-Specific Barriers/Mechanisms

The Third Line of Defense

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Third Line of Defense Consists of mechanisms

and agents that target specific antigens Via the use of

lymphocytes.

Over Active Immune System

Allergies

An allergy is an oversensitivity to a normally harmless antigen.

Harmless antigens, that cause the over-the-top response, are known as allergens. Food

Peanuts Airborne

Pollen Pet dander Mold

Chemical Penicillin Jewelry metals

Review