Question

How are blood types determined?

Answer 1

Red blood cells of the individual have different types of antigens (agglutinogens). Depending on the types of agglutinogen present there are four types of blood groups:

1. A group - containing ‘A’ agglutinogens.
2. B group - containing ‘B’ agglutinogens.
3. AB group – containing both ‘A’ and ‘B’ agglutinogens
4. group – Not containing either ‘A’ or ‘B’ agglutinogens

‘A’ group person’s serum contains anti-B agglutinins

‘B’ group person’s serum contains anti-A agglutinins

‘AB’ group person’s serum does not contain any of the above agglutinins

‘O’ group person’s serum contains both anti-A and anti-B agglutinins.

Apparatus and reagents

1. Glass Slide.
2. Dropper.
3. Special porcelain tile with 12 depressions.
4. Normal Saline.
5. Anti-A serum.
6. Anti-B serum.
7. Anti-D serum.
8. 1% sodium citrate prepared in normal saline.
9. Spirit.

Procedure:

1. 3-4 drops of sodium citrate solution are put in one of the depression on the porcelain tile. It is labeled ‘D’
2. With usual aseptic precaution finger is pricked and two drops of blood are mixed with sodium citrate solution placed in the depression. Thus red blood cell suspension is obtained. It is mixed well.
3. Two drops of ant-A serum, anti-B serum, and normal saline are put in three different depression and they are labeled ‘A’, ‘B’ and ‘C’.
4. Two drops of cell suspension (from D) are put in each of these depression (A, B and C). It is mixed well by blowing.
5. After 15 minutes A, B and C depression are observed for presence or absence of agglutination.
6. ‘C’ depression acts as a control (for comparing between agglutination and no agglutination). In depression ‘C’ agglutination does not occur. If by chance agglutination occurs in this control, whole procedure is to be repeated.
7. Blood group is determined as follows-

Anti A	Anti B	Blood Group
Agglutination	No agglutination	A group
No agglutination	Agglutination	B group
Agglutination	Agglutination	AB group
No agglutination	No agglutination	O group

Taking a drop from each depression on the slide and observing the slide under the microscope confirm agglutination.

VII. By using Anti D-serum, Rh group is determined.