The ABO blood group antigen epitopes are carbohydrates present on a cell membrane protein. The basic core carbohydrate (known as H) is present in group O individuals. Group A and group B individuals carry different saccharide additions to the basic core. Group AB individuals carry both the additional saccharides (on different core carbohydrates).

This experiment investigates the structure of the ABO antigens and should allow you to deduce what inherited factors produce these antigens.

Group O red blood cells have been incubated with either UDP-galactose or UDP-N-acetyl galactosamine together with group A, group B or group O serum for six hours at 37^oC as follows:

Tube 1        Tube 2        Tube 3        Tube 4        Tube 5        Tube 6

Group O       Group O       Group O       Group O       Group O       Group O

cells            cells             cells             cells             cells             cells

UDP-NacG     UDP-Gal        UDP-NacG     UDP-Gal        UDP-NacG     UDP-Gal

O-serum       O-serum       B-serum       B-serum       A-serum       A-serum

Mix 10 ml of cells from each tube with 10 ml group O serum on a microscope slide, and check for agglutination.

Record your results.

Here are the results of the experiment

Tube 1         Tube 2         Tube 3         Tube 4         Tube 5         Tube 6

Group 0 Cells Group 0 Cells Group 0 Cells Group 0 Cells Group 0 Cells Group 0 Cells

UDP-NacG     UDP-Gal        UDP-NacG     UDP-Gal        UDP-NacG     UDP-Gal

0-Serum       0-Serum       B-Serum       B-Serum       A-Serum       A-Serum

Agglutination          No      No      No      Yes     Yes     No

No agglutination was observed with tube 1, 2, 3 and 6

Agglutination was observed with tube 4 and 5

The Labororatory report- It should contain:

• The AIM of the experiment

                   Why you are doing it

• The Experimental Procedure

                   How you did it

• The Results

What you observed

• The Discussion and Conclusion

                   What it means

• Include references at the end.

You should consider the following

1. What sugar is added to the basic core carbohydrate to produce

a) the group A epitope?

b) the group B epitope?

2. Why does a group A individual produce the group A  epitope while a group O individual does not?

3. What do you think is the inherited factor which determines that an individual is group O, A, B, or AB? (Remember that group O is a recessive characteristic.)

4. Write an equation for the enzyme reaction by which the Group A and Group B saccharide residues are added to the core carbohydrate.

(Hint: look up the mechanism of synthesis of glucogen in a biochemistry textbook.)

5. Look up the structures of the ABO antigen epitopes.