How Are Antibodies Used for Blood Typing?

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Project Summary

Difficulty	4
Time required	Very Short (a day or less)
Prerequisites	None
Material Availability	Specialty items
Cost	Low ($20–$50)
Safety	No issues

Sponsor

Sponsored by a generous grant from Bio-Rad

Objective

This project has two objectives:

1. Identify the unknown "blood types" of the synthetic samples.
2. Understand the importance of blood typing when transfusions are necessary for medical treatment.

Introduction

The human immune system has various ways of responding to an infection caused by bacteria or viruses. Our bodies produce proteins (antibodies) that are highly specific for the infectious agent as a part of our "humoral" immune response. The antibodies help stop the infection from spreading further and help to eliminate the bacteria or virus from the body.

Antibodies are also used to help our bodies find and destroy "foreign" cells such as tumors. Because antibodies bind tightly to only one type of structure on the surface of cells (antigen), they can also be useful for identifying different types of blood cells. It is important to correctly identify blood cells in our bodies if we ever need to receive blood from someone else because we are sick (transfusion).

Our blood type is determined based on the presence or absence of two proteins on the surface of our red blood cells (Type A and Type B). There are four possible combinations of blood types namely: Type A, Type B, Type AB, and Type O (contains neither A nor B proteins). This is referred to as the ABO blood type. In addition, red blood cells have a Rhesus factor or Rh, which is either present or absent. If the Rh factor is present, the cells are referred to as Rh positive. Including both the ABO and Rh systems for blood typing, there are a total of 8 possible blood types that are shown in Table 1. The table also shows approximately what percentage of the U.S. population is each blood type.

Blood types are determined by using antibody reagents that specifically react with the A, B, and Rh proteins on the surface of red blood cells. First, three drops of blood are placed on a microscope slide. Next, a drop of anti-A reagent is added to one drop of blood, a drop of anti-B reagent is added to the second drop of blood and a drop of anti-Rh reagent is added to the third drop of blood. The slide is gently rotated and examined for clumping (agglutination). If clumps are seen in the anti-B and anti-Rh reagents, then the person's blood is considered "B positive."

When you donate blood, your blood type is determined (usually by the American Red Cross) and is used to match your blood with someone who needs it. If someone got the wrong blood type during a transfusion, they could have a very severe reaction. Type O negative blood is considered the "universal donor" because anyone can receive that blood type without having a reaction. Type AB positive is considered the "universal recipient" because someone with that blood type can receive blood from anyone else without having a reaction.

Terms, Concepts and Questions to Start Background Research

In order to do this project, you should conduct background research that enables you to understand the following terms and concepts:

• Plasma
• White blood cell
• Red blood cell
• Agglutination
• Blood type
• Antibody
• Antigen
• Humoral immune response
• Transfusion

Bibliography

• "I would like to donate blood—do they need all blood types or just certain ones?":
  http://science.howstuffworks.com/question593.htm
• "How the Immune System Works":
  http://science.howstuffworks.com/immune-system.htm
• Information on Blood Types (this entry is from the Microsoft® Encarta® Online Encyclopedia 2005, http://encarta.msn.com ©1997-2005 Microsoft Corporation. All Rights Reserved.):
  http://encarta.msn.com/encyclopedia_761564042/Blood_Type.html
• Hyde, RM and Patnode, RA. (1978) Immunology Reston Publishing Co, Inc., Reston, VA.
• Lehninger, AL. (1978) Principles of Biochemistry Worth Publishers, New York, pp. 323-325.
• Smith, EL, et al. (1983) Principles of Biochemistry: Mammalian Biochemistry McGraw-Hill Book Company, New York, pp. 78-81.

Materials and Equipment

This project uses Carolina Biological Supply Company kit #70-0101 ($24.95). It can be purchased from:
Carolina Biological Supply Company
2700 York Road
Burlington, NC 27215
800-334-5551
Fax: 800-222-7112
www.carolina.com

Experimental Procedure

1. Using the dropper vial, place a drop of the first synthetic blood sample in each well of the blood typing slide. Replace the cap on the dropper vial. Always replace the cap on one vial before opening the next vial to prevent cross contamination.
2. Add a drop of synthetic anti-A (blue) to the well labeled A. Replace the cap.
3. Add a drop of synthetic anti-B serum (yellow) to the well labeled B. Replace the cap.
4. Add a drop of synthetic anti-Rh serum (clear) to the well labeled Rh. Replace the cap.
5. Using a different color mixing stick for each well (blue for anti-A, yellow for anti-B, white for anti-Rh), gently stir the synthetic blood and anti-serum drops for 30 seconds. Remember to discard each mixing stick after a single use to avoid contamination to your samples.
6. Carefully examine the thin films of liquid mixture left behind. If a film remains uniform in appearance, there is no agglutination. If the sample appears granular, agglutination has occurred. Determine the blood type of the sample based on the examples given in the data table below. Answer yes or no as to whether agglutination occurred in each sample. A positive agglutination reaction indicates the blood type.
7. Record the results for the first blood sample in the data table.
8. Thoroughly rinse the blood typing slice, then repeat steps 1 through 7 for synthetic blood samples 2, 3, and 4.

Variations

• What happens if you mix two different synthetic blood samples together?
• What happens if you mix two different antibody reagents together?
• What happens if you don't mix the slide well after adding all the reagents?
• Is the agglutination reaction affected by temperature?
• If you mix the slide for longer times does the agglutination disappear?

• For more science project ideas in this area of science, see Biotechnology Project Ideas

Credits

Last edit date: 2008-08-10 22:00:00