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How Are Antibodies Used for Blood Typing?

Difficulty
Time Required Very Short (≤ 1 day)
Prerequisites None
Material Availability A kit containing specialty items is needed for this science project. See the Materials tab for more details.
Cost Average ($40 - $80)
Safety No issues

Abstract

Have you ever heard about different blood types? Do you know what your blood type is? Antibodies help scientists determine different human blood types. This project is a practical introduction to the human immune system in which you will learn about what antibodies are, how they are formed, and how they can be used to identify different types of cells.

Objective

Identify the unknown "blood types" of the synthetic samples and determine if any of the samples are compatible as donor-recipient pairs for a blood transfusion.

Credits

Author: Mark A. Schenerman, Ph.D. (MedImmune)
Editor: Andrew Olson, Science Buddies

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Last edit date: 2014-04-21

Introduction

The human immune system has various ways of responding to an infection caused by pathogens like bacteria, viruses, or fungi. 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 pathogen 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 (antigens), 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 (transfusion) because we are sick.

Our blood type is determined based on the presence or absence of two proteins, antigen A and antigen B, on the surface of our red blood cells. There are four possible combinations of blood types namely: Type A (only antigen A), Type B (only antigen B), Type AB (both antigens A and B), and Type O (neither antigens A nor B). This is referred to as the ABO blood typing system. 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, which are shown in Table 1, below, along with a summary of how to determine blood type based on whether the antigens and Rh factor are present.

Blood TypeAntigen A PresentAntigen B PresentRh Factor Present
O positiveNoNoYes
A positiveYesNoYes
B positiveNoYesYes
O negativeNoNoNo
A negativeYesNoNo
AB positiveYesYesYes
B negativeNoYesNo
AB negativeYesYesNo

Table 1. Blood Types & Presence of Antigens and Rh Factors for Each

Table 2, below, shows these blood types along with approximately what percentage of the U.S. population is each blood type.

Blood Type% of U.S. Population
O positive38
A positive34
B positive9
O negative7
A negative6
AB positive3
B negative2
AB negative1

Table 2. Blood Types & Proportion of U.S. Population for Each 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 but not the anti-A reagent, 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.

In this project you will use synthetic blood samples, provided in the kit, to determine the blood type from four different people. Based on their blood types would any of the four people make good donor-recipient pairs for a blood transfusion?

Terms and Concepts

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

  • Antibody
  • Humoral immune system
  • Antigen
  • Transfusion
  • Blood type
  • Rhesus factor
  • Agglutination
  • Red blood cells
  • Plasma

Questions

  • The blood types in the Introduction are for red blood cells. There are other cell types in your blood though. What are the other cell types and do they have the same blood typing systems?
  • What blood type is needed for a transfusion for a Type O positive patient?
  • What would happen if someone was transfused with an incompatible blood type?

Bibliography

Materials and Equipment Product Kit Available

This project uses a Science Buddies kit. The kit includes all the materials needed to carry out this experiment. Inside the kit you will find:

  • Blood typing slide (1)
  • Antisera A and B
  • Anti-Rh factor
  • Mixing sticks
  • Synthetic blood samples (4); Note: These do not contain real blood and thus are completely safe to handle. They will however accurately simulate the blood typing process.
  • Disposable plastic pipettes (4); these are for moving the blood samples to the blood typing slide
  • Chemical splash goggles
  • Disposable gloves
  • Lab notebook

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Project Kit: $44.95

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Experimental Procedure

  1. In your lab notebook make a data table, like Table 3 below, to record all your data and observations.
Trial Number Sample Number Reaction with
Anti-A (Y/N)
Reaction with
Anti-B (Y/N)
Reaction with
Anti-Rh (Y/N)
Determined Blood Type
(from Table 1, in the Background tab)
11    
 2    
 3    
 4    
21    
 2    
 3    
 4    
31    
 2    
 3    
 4    
Table 3. You will need a data table like this to record your data.
  1. Using a disposable plastic pipette, place a drop of synthetic blood sample #1 in each well of a blood typing slide.
  2. Add a drop of synthetic anti-A to the well labeled A.
  3. Add a drop of synthetic anti-B serum to the well labeled B.
  4. Add a drop of synthetic anti-Rh serum to the well labeled Rh.
  5. Using a different color mixing stick for each well, gently stir the synthetic blood and antiserum drops for 30 seconds. Remember to discard each mixing stick after a single use to avoid contamination to your samples.
  6. After 30 seconds of stirring carefully examine the liquid in the wells.
    1. If the liquid is clear or light pink with no particles or cloudiness formed, then no reaction has occurred and you should mark "No" in the appropriate box in the data table.
    2. If there are solid particles that have formed in mixing the sample or antiserum (they may be darker or lighter than the original liquid), then a reaction has occurred and you should mark "Yes" in the appropriate box. Also, if the liquid has very small particles formed, giving a cloudy appearance to the liquid, then a reaction has occurred and you should mark "Yes" in the appropriate box.
    3. It is important to look very closely at the wells and only do one well at a time. Be sure to stir at least 30 seconds with the plastic stick. The final product may be clear, white or dark pink depending on the combination of blood sample and antiserum, so look carefully to see if small or large particles have formed in the well.
    4. Reference the photos in Figure 1 below for help determining if a reaction has occurred or not. If you continue to have trouble read the FAQ for this project.
typing of blood samples
Biotechnology science project
Figure 1. If the antiserum does not cause agglutination the sample will be free of floating particles like the picture on the left. If the antiserum does cause a reaction the sample will turn cloudy and you will see particles form as shown in the picture on the right.
  1. Record the results for the first blood sample in the data table.
  2. Thoroughly rinse the blood typing slide, then repeat steps 2 through 8 for synthetic blood samples 2, 3, and 4. Use a different pipette for each synthetic blood sample to prevent cross contamination.
  3. Repeat steps 2 through 9 two more times so that you have done a total of three trials.
  4. Once you have determined the blood type for each sample (by referring to Table 1, in the Background tab), you are ready to look at the data like a doctor. Would any of the samples make good donor-recipient pairs for a blood transfusion? Why or why not?

Troubleshooting

For troubleshooting tips, please read our FAQ: How Are Antibodies Used for Blood Typing?.

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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?

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Frequently Asked Questions (FAQ)

If you are having trouble with this project, please read the FAQ below. You may find the answer to your question.
Q: I can't tell if a reaction has occurred, help!
A: Make sure you have stirred the liquid for at least 30 seconds and not more than 45 seconds. You may need to let it sit for a few seconds after you stop stirring to see if any cloudiness or particles will form. The particles may be large and colored or colorless, or the liquid may turn cloudy with small particles. These both indicate a reaction has occurred. Look very closely at the liquid; look at it under different lights. Don't hesitate to repeat trials until you get consistent results; there is enough in the kit. You could try using two drops of blood sample and two drops of antiserum. Make sure the drops are at least as large as a pencil eraser. The final product may be clear/white or light or dark pink depending on the combination of blood and antiserum.
Q: The blood samples are slightly different colors. Is that normal?
A: Yes, that is normal; some of the blood samples will appear darker than others. This will not affect the final results. Remember that the "reaction" between antiserum and blood sample can be different colors. The important thing is if it turns cloudy or particles form (a precipitate).
Q: My results show all the same blood type. Is that right?
A: There must be a problem! The samples are not all the same, so if you're getting the same result for every sample, something must be going wrong! Read details on how to determine if a reaction has occurred, and reference the Figure 1 in the Procedure of the Project Idea. Repeat your trials at least 3 times, and you will hopefully begin to get consistent results.
Q: I'm getting different results each time. Why?
A: Make sure to properly rinse your well plates and stirring sticks between trials! Also remember that each antiserum has a corresponding stirring stick color. Make sure you are looking very closely at the wells to determine if a reaction has occurred. Make sure you are reading the blood type chart on the Project Idea correctly and that you are entering data correctly on the data table. Are your drops of sample and antiserum large enough? They should be at least as large as a pencil eraser, if not larger. Make sure to use equal quantities of sample and antiserum. One final piece of advice is be persistent and patient! Don't be afraid to do more than three trials until you get consistent results.

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