Immune System

Immune System

Middle School

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Learning Objectives

• Understand the primary functions of the immune system.

• Identify the key structures involved in the body's defense.

• Describe the body's three lines of defense against pathogens.

• Explain the difference between active and passive immunity.

• Describe how vaccines work to protect the body from disease.

Key Vocabulary

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Pathogen

An organism, like a virus or bacterium, that has the potential to cause disease in the body.

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Antigen

A foreign substance that enters the body and triggers a defensive response from the immune system.

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Antibody

A protein made by the immune system to find and neutralize specific antigens in the body.

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Lymphocyte

A type of white blood cell that is essential for the immune system's specific defense response.

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Phagocyte

A type of white blood cell that surrounds and absorbs bacteria and other small, harmful particles.

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Vaccine

A substance with weakened pathogens used to stimulate antibody production and provide immunity against diseases.

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Function and Structures of the Immune System

• The immune system defends the body against harmful invaders called pathogens.

• It identifies foreign substances, called antigens, to trigger an immune response.

• The skin acts as a physical barrier to block most pathogens.

• Bone marrow produces white blood cells (WBCs), which create antibodies to fight pathogens.

• The spleen filters the blood.

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Multiple Choice

What is the primary role of bone marrow in the immune system?

• It acts as a physical barrier to block pathogens.

• It produces white blood cells and antibodies.

• It filters damaged cells and pathogens from the blood.

• It traps pathogens that enter the respiratory system.

The Body's Three Lines of Defense

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First Line of Defense

• The skin acts as a physical barrier blocking pathogens

• Mucous membranes traps and expels pathogens through coughing and sneezing

• Enzymes in sweat, saliva and stomach acids kill harmful invaders

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Second Line of Defense

• This is a general attack known as the inflammatory response.

• White blood cells called phagocytes move in to destroy invading pathogens.

• A fever raises body temperature, which can help the body fight infection.

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Third Line of Defense

• This is a highly specific defense that remembers pathogens for the future.

• T-cells identify pathogens, and B-cells are activated to produce antibodies.

• Antibodies attach to and neutralize a specific pathogen.

• Memory cells allow the body to react faster to future infections.

Multiple Choice

Which line of defense involves B-cells and T-cells that target specific pathogens?

• First Line of Defense

• Second Line of Defense

• Third Line of Defense

• All of the above

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Types of Immunity

Active Immunity

• Your own immune system produces antibodies in response to a pathogen, providing long-lasting protection.

• This can happen naturally after an infection, as your body fights off a live pathogen.

• Vaccination also provides active immunity by introducing a weakened or inactive form of a pathogen.

Passive Immunity

• You are given antibodies from an outside source instead of your body producing them.

• This type of immunity is temporary because your body does not create its own memory cells.

• Examples include antibodies passed from a mother to her baby or through an antibody injection.

Multiple Choice

How do vaccines provide immunity?

• They introduce antibodies directly into the body to fight disease.

• They strengthen the skin to prevent pathogens from entering.

• They introduce a weakened pathogen so the body can produce its own antibodies.

• They give the body a temporary dose of passive immunity.

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Common Misconceptions

Misconception	Correction
Antibiotics are effective at killing viruses.	Antibiotics only fight bacterial infections and have no effect on viruses.
A fever is a sign that your immune system is failing.	A fever often means your immune system is working hard to fight infection.
Vaccines can give you the disease they are meant to prevent.	Vaccines use weakened or killed pathogens that cannot cause a full-blown illness.

Multiple Choice

What is the key difference between the non-specific inflammatory response and the specific immune response?

• The non-specific response uses antibodies, while the specific response uses phagocytes.

• The non-specific response is the first line of defense, while the specific response is the second.

• The non-specific response treats all pathogens the same, while the specific response targets a particular pathogen.

• The non-specific response creates memory cells, while the specific response causes fever.

Multiple Choice

Which statement about passive immunity is TRUE?

• It results from the body's own production of antibodies and memory cells.

• It provides long-lasting protection by activating the immune system’s memory.

• It involves receiving antibodies from an outside source and is temporary.

• It can only be acquired through vaccination.

Multiple Choice

A person is vaccinated against Measles. A year later, they are exposed to the virus. How will their body's immune response to the virus differ from its initial response to the vaccine?

• The response to the virus will be slower and weaker than the response to the vaccine.

• The body will have to learn how to fight the virus from scratch.

• The response will be identical to the primary response to the vaccine.

• The response to the virus will be much faster and stronger due to memory cells created from the vaccine.

Multiple Choice

Which statement correctly describes the roles of antigens, B-cells, and antibodies in the immune response?

• Antigens produce B-cells, which then transform into antibodies.

• Antibodies detect antigens, which then signal B-cells to attack.

• B-cells are a type of antigen that produces antibodies to fight pathogens.

• B-cells identify specific antigens and then produce antibodies designed to neutralize them.

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Summary

• The immune system defends the body against pathogens using three lines of defense.

• Key parts of the immune system include the skin, bone marrow, and spleen.

• T-cells and B-cells create antibodies and memory cells for a specific response.

• Active immunity is long-lasting, while passive immunity is a temporary defense.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4