Materials Included In Kit

Additional Materials Required

Prelab Preparation

1. Laminate the Antigen Templates to increase durability.
2. Cut out each of the four antigens (2 copies of each) and place in an accessible location for all students.

Safety Precautions

This classroom activity is considered nonhazardous. Remind students of the importance of exercising caution when working with scissors.

Lab Hints

• This kit comes with 30 Antibody Regions Model Sheets and two copies of each antigen. The prelaboratory assignment may be completed before coming to lab, and the post lab may be completed the day after the lab.
• Students will share the antigen templates. Once students have constructed their antibodies, place the antigen templates where they are easily accessible to all students so the matching antigen may be determined.
• The instructor may wish to check that students correctly matched the antibody with its corresponding antigen after step 8.
• A variation of this lab may also be done by making copies of the antigen cards and giving one card to each student. Have each student act as his or her immune system would and produce the matching antibody to destroy the antigen.

Answers to Prelab Questions

1. Explain activation in your own words.

   Activation occurs when an antibody binds with the epitope of its matching antigen. This causes many more copies of the antibody to be produced so that the remaining invading antigens are also eliminated.

2. Refer to Figures 1 and 2 in the Background section. Each arm shown in Figure 1 is able to bind one antigen. How many antigens can each antibody in Figure 2 bind?

   IgM is able to bind to ten antigens, IgG, IgD and IgE are able to bind to two antigens and IgA is able to bind to four antigens.

Answers to Questions

Antibody Function Worksheet

Post-Lab Questions

1. Draw a sketch of the (completed) model antibody that you constructed.

   See Antibody Model Answer Key in Teacher PDF.

2. Did the antibody “fit” or bind with any of the suspect antigens? If so, sketch the bond antibody–antigen complex to show the “fit.”

   See Antibody/Antigen Model Answer Key in Teacher PDF.

3. Describe the next steps in the antibody life cycle for a) an antibody that matched or binded with with an antigen, b) an antibody that did not match any of the antigens.

   Since the antibody matched the E. coli antigen it will go through activation. Activation results in several more copies of the antibody which tag the foreign antigens for destruction. If the antibody did not match any antigens the antibody will be eliminated as it has no purpose if there are no matching antigens to tag for destruction.

4. Sarah had chicken pox at age 8. Five years later her brother Ryan also contracted chicken pox. Why is Sarah not at risk of getting chicken pox again?

   When Sarah had chicken pox her body produced antibodies which recognize the chicken pox antigen. Therefore, the many copies of the antibody were able to tag the chicken pox antigen for destruction before it could infect Sarah again.

5. Why do some vaccinations require boosters after a certain amount of time to maintain immunity whereas others require only one initial dose of the vaccine?

   Vaccinations require boosters because the body is not regularly exposed to the antigen which the vaccination protects against. Therefore the antibody is not signaled to produce more copies. Other vaccinations do not require boosters because the antibodies are regularly exposed to the antigen which causes several more copies to be made.

Teacher Handouts

10974_Teacher1.pdf

References

Special thanks to Dr. William P. Baker, Southwestern College, Phoenix, AZ, for providing the idea for this activity to Flinn Scientific.

Campbell, N. A. Biology, 6th Ed.; Benjamin Cummings: San Francisco, 2002.

Introduction

The body is constantly exposed to microbes, toxins, dust and pollen. These substances are potentially harmful and may even cause disease if they are not eliminated from the body. One of the most important strategies the body uses to fight these hazards is the production of antibodies. Construct your own antibody and witness how it works to destroy antigens.

Concepts

• Antibodies
• Antigens
• B-cells

Background

Antibodies are glycoproteins found in the blood and other body fluids of vertebrates. A vital part of the immune system, antibodies are produced by B-cells and belong to a class of proteins called immunoglobulins (Ig). The main function of antibodies is to recognize and initiate the removal of foreign objects, such as bacteria or viruses. Each antibody molecule consists of four polypeptide chains—two identical heavy chains and two identical light chains. The heavy and light chains are joined together by disulfide bridges to form a Y-shaped protein molecule (see Figure 1).

There are several types of antibody heavy chains as well as several different types of antibodies. Antibodies are grouped into five categories known as isotypes based on their heavy chain structure and their location and function in the body (see Figure 2). Within each isotype the two heavy chains and the two light chains are the same. Variation within a specific isotype, for example, due to differences in an area appropriately named the variable region. This region at the tip of the antibody is extremely variable allowing millions of different antibodies to exist within each isotype. Both the heavy chain and the light chain have a variable region (v). This diversity of the variable regions allows the immune system to recognize a multitude of antigens.

Antigens are foreign substances or materials, such as bacteria or viruses, that do not belong to the host organism. Antibodies recognize and bind to a specific region of the antigen called the epitope. Once the antibody binds to the antigen, the antigen is tagged to be destroyed by the immune system. The fit between the antigen-binding site of the antibody and the epitope of the antigen is highly specific. This specificity allows antibodies to bind only with their matching antigen so other substances are not tagged for destruction.

In order for an antibody to survive it must combine with an antigen and undergo activation. Activation causes rapid proliferation of antibody-secreting cells by mitosis, resulting in the production of more copies of the antibody which tag the remaining matching antigens for destruction. The body constantly produces millions of antibodies. Those antibodies that do not match antigens are not needed and never undergo activation so they are eliminated.

Experiment Overview

The purpose of this activity is to build a model antibody from the class IgG isotype. Simulate the life cycle of an antibody by determining if it matches an antigen or not and analyzing the steps throughout the process.

Materials

Prelab Questions

1. Explain activation in your own words.
2. Refer to Figures 1 and 2 in the Background section. Each arm shown in Figure 1 is able to bind one antigen. How many antigens can each antibody in Figure 2 bind?

Safety Precautions

This activity is considered nonhazardous. Exercise caution when working with scissors.

Procedure

1. Obtain the Antibody Regions Model Sheet.
2. Using scissors, carefully cut out the IgG Constant Regions Model. Note: Do not cut off the dashed lines at the ends of the heavy and light chain regions.
3. Using the Antibody Regions Model Sheet, select a heavy chain variable region (HV) and light chain variable region (LV) for the antibody.
4. The heavy chain variable region (HV) contains three pairs of heavy chains. Choose one matching HV pair and cut it out with scissors. Note: Do not cut off the dashed lines or tabs at the ends of the HV.
5. The light chain variable region (LV) contains two pairs of light chains. Choose one matching LV pair and cut it out with scissors. Note: Do not cut off dashed lines or tabs at the ends of the LV.
6. Match the dashed lines on the HV to the dashed lines on the HC. Tape the HV to the HC to secure fragments.
7. Repeat step 6 using the LV and LC.
8. Examine the representative or sample antigens on the Antigen Templates Sheet. Examine whether your completed antibody molecule will “fit” or bind with one of the antigens. Determine if the antibody is a match for any of the antigens.
9. Complete the Antibody Function Worksheet.

Student Worksheet PDF

10974_Student1.pdf