Nature: The Human Body 3

– The Immune System –

The human immune system is a complex network of cells, tissues, and organs that work in harmony to protect the body from harmful pathogens. Functioning as the body’s defense mechanism, it plays a critical role in maintaining health and preventing diseases.

When foreign substances like bacteria, viruses, or toxins invade the body, the immune system springs into action. White blood cells, the soldiers of the immune system, recognize these invaders and initiate a response. Some white blood cells, known as phagocytes, devour the intruders, while others, called lymphocytes, remember the pathogens and enable a faster response in future encounters.

However, the immune system is not infallible. Sometimes, it fails to recognize harmful substances, leading to infections. Alternatively, it might wrongly identify harmless substances as threats, causing allergies. In more severe cases, it can even attack the body’s own cells, leading to autoimmune diseases.

Despite these potential issues, the immune system, in most cases, successfully protects the body, highlighting the impressive capabilities of biological systems in preserving human health.

Choose NO MORE THAN TWO words from the text for each answer.

The human immune system is a complex ______ of cells, tissues, and organs that work together to protect the body.
The immune system’s main function is to act as the body’s ______ mechanism against harmful pathogens.
When the body is invaded by foreign substances, the immune system ______ into action.
White blood cells, specifically phagocytes, consume the ______.
Lymphocytes play a critical role by remembering the ______ for a faster response in future encounters.
The immune system may sometimes attack the body’s own cells, leading to ______ diseases.

Choose NO MORE THAN ONE word from the text for each answer.

The human body is equipped with an intricate network known as the immune system, functioning as a ______ mechanism against disease-causing organisms. Whenever foreign invaders such as bacteria, viruses, or toxins intrude, this system activates its ______, mainly white blood cells. Certain types, called phagocytes, ______ and eliminate these intruders, whereas lymphocytes keep a record of the pathogens for swift ______ in future invasions. However, the immune system may occasionally fail, either by not recognizing harmful substances, which leads to infections, or by wrongly attacking the body’s cells, causing ______ diseases. Nonetheless, it generally succeeds in safeguarding human health, reflecting the ______ capabilities of biological systems.

Vocabulary Builder

Find the synonyms (words with the same or similar meaning) to these 9 words from the original passage.

Original Word	Variants Used
complex	____________________
network	____________________
protective	____________________
pathogens	____________________ / ____________________
triggers	____________________
harmful	____________________
consume	____________________
pathogens	____________________
autoimmune	____________________

Reveal answer (7 More Words)

Original Word	Variants Used
complex	intricate
network	system
protective	safeguarding
pathogens	foreign invaders, harmful substances
triggers	activates
harmful	disease-causing
consume	eliminate
pathogens	intruders
autoimmune	wrongly attacking