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Defending Against Microbes

Defending Against Microbes

A CDC nurse extracting influenza virus vaccine from a 5 mL vial.
Courtesy of the CDC/James Gathany.

  • Grades:
  • Length: 60 Minutes


Students investigate the human immune system and solve a crossword puzzle featuring vocabulary related to the immune system and microbes.

This activity is from The Science of Microbes Teacher's Guide, and is most appropriate for use with students in grades 6-8. Lessons from the guide may be used with other grade levels as deemed appropriate.

The guide is available in print format.

This work was developed in partnership with the Baylor-UT Houston Center for AIDS Research, an NIH-funded program.

Teacher Background

We are surrounded by potential disease-causing microbes, yet most of us remain remarkably healthy. How do our bodies protect themselves against infections by microorganisms and viruses? The answer lies with the remarkable immune system, which consists of many types of proteins, cells, organs and tissues—all working together to identify and destroy foreign invaders (primarily microbes) and abnormal cells (such as tumor cells) within the body.

A healthy immune system can distinguish between the body’s own cells (including helpful microbes inside the body) and foreign cells. When immune system cells detect foreign cells or organisms, they quickly attack. Anything that triggers this immune response is called an “antigen.” An antigen can be a microbe, a part of a microbe, or even cells from another organism (such as from another person). Parts of the immune system also can remember a disease-causing agent (or pathogen) and mount an attack if the pathogen reappears. These immunological memories are the basis of vaccination. Vaccines “teach” the immune system to recognize a specific pathogen by mimicking a natural infection by that pathogen.

Objectives and Standards


  • Communicate scientific procedures and explanations.

Life Science

  • Living systems at all levels of organization demonstrate the complementary nature of structure and function.

  • The human organism has systems for protection from disease.

  • Disease is a breakdown in structures or functions of an organism. Some diseases are the result of intrinsic failures of the systems. Others are the result of damage by infection by other organisms.

Materials and Setup

Materials per Group of Students

  • Set of colored highlighters (at least one marker per student)

  • 4 copies of each student sheet (see Lesson pdf)

  • Group concept maps (ongoing)


Make copies of the student sheets. Have students work individually or in groups of four.

Procedure and Extensions

  1. Ask students, If microbes are everywhere, why aren’t we sick all the time? Conduct a class discussion or make a list of students’ ideas on the board. If not mentioned by students, introduce the idea that the body’s defense system—called the immune system—helps to find and destroy microbes.

  2. Distribute a copy of the "Germ Defense" article to each student. Have students read the article individually and then discuss it within their groups. Students should use their markers to highlight new words or concepts they find in the article.

  3. Within their groups, have students discuss the words or concepts they highlighted. Encourage groups to search the Internet for additional, related information. Reliable websites include the National Institutes of Health ( and the Centers for Disease Control and Prevention (

  4. Distribute the "Attackers & Defenders" student sheet. Have students use what they have learned to complete the crossword puzzle, individually or in groups.

  5. Allow time for students to add to their concept maps.

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Science Education Partnership Award, NIH

Science Education Partnership Award, NIH

Grant Number: 5R25RR018605