Question:

Is HIV a communicable or non-communicable disease? 

Explain your reasoning.

Directions: Please write this on the left hand page of your medical journal, after copying the Lesson # and Lesson Title.  

Which student response is incorrect? 

Explain in detail why it is incorrect. 

3 sentence minimum. 

The Three Levels of Immunity

Every day, your body is exposed to bacteria, viruses, and other harmful organisms. Most of the time, you do not even realize it. That is because your immune system works constantly to protect you. Scientists often describe immunity as working in three levels of defense. Each level plays a different role in keeping the body healthy.

First Level of Defense: Physical and Chemical Barriers

The first level of immunity is your body’s outer protection. This level works to prevent pathogens from ever entering the body.

Your skin acts as a physical barrier that blocks most microorganisms. If your skin is not broken, many pathogens cannot get inside. Mucus in your nose and throat traps particles from the air, and tiny hair-like structures called cilia move trapped pathogens out of the respiratory system. Tears, sweat, and saliva contain chemicals that can destroy bacteria. Stomach acid is strong enough to kill many pathogens that enter through food or water.

This level is always working and does not target specific pathogens. It simply keeps most invaders out.

Second Level of Defense: Innate Immune Response

If a pathogen gets past the first level, the second level of immunity is activated. This is called the innate immune response.

White blood cells play an important role at this level. Some white blood cells, such as macrophages, surround and digest pathogens in a process called phagocytosis. Inflammation may occur in the infected area. You might notice redness, warmth, swelling, or pain. These symptoms happen because blood flow increases to the area, bringing more immune cells to fight the infection.

This level still does not target one specific pathogen. It responds the same way to many different types of invaders. It acts quickly but does not provide long-term protection.

Third Level of Defense: Adaptive Immune Response

The third level of immunity is called the adaptive immune response. This level is highly specific and targets particular pathogens.

Certain white blood cells called B cells produce antibodies. Antibodies are proteins that bind to specific antigens on a pathogen. This helps destroy the pathogen or mark it for destruction by other immune cells. 

One important feature of the third level is memory. After the body fights off a pathogen, memory cells remain. If the same pathogen enters the body again, the immune system responds faster and more effectively. This is how vaccines help protect people from diseases. Vaccines safely expose the body to a dead or weakened pathogen so memory cells can form without causing serious illness.

Why All Three Levels Matter

The immune system works like a team. The first level tries to keep pathogens out. The second level attacks quickly if something gets in. The third level provides a targeted attack and long-term protection.

Together, these three levels allow the body to defend itself every day, often without you even knowing it.

As you know, our patient, Maria Lopez, needs a new kidney. Maria's kidneys were first badly damaged when she became infected by Malaria as a baby. Malaria is a parasite that is transmitted by mosquitos. Malaria can damage the kidneys by causing inflammation and impairing blood flow. This can lead to acute kidney injury (AKI) and chronic kidney disease. This was made worse by her high blood pressure. 

TNT #1: Question: Discuss how the three levels of immunity tried to protect Maria from Malaria as a baby. Hint: Start with the skin and end with antibodies.