Human immune system

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Biology 2201

Unit 3 – Dynamic Equilibrium

Section 6- Immune System

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What is Immunity?

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Immunity

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 nonharmful organisms and produces an appropriate response.

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Foreign Invaders

Called Pathogens

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

Antigens

Toxins that pathogens produce that cause harm to an organism.

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Parts of the Immune System

Blood - White Blood Cells in particular.

Lymph nodes

Thymus Gland – Produces T Lymphocytes

Bone Marrow – Produces B Lymphocytes

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How does the body fight infection/foreign invaders?

The Body’s THREE 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

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Second Line of Defense – Nonspecific Immune Response

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.

Macrophage: A phagocytic cell found in the liver, spleen, brain and lungs. Travels

to all areas of the body to find and eat pathogens.

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This is a specific response to a specific pathogen/antigen.

The response involves the creation of Antibodies.

Third Line of Defense – Specific Immune Response

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Antibodies

Y-shaped protein molecule.

Made up of variable and constant regions.

Made up of Heavy and Light chains.

Produced by B-Lymphocytes

Function: Recognize antigens, bind to and deactivate them.