In the blood typing procedure what causes agglutination of red blood cells?

1 Answer
Nov 24, 2016

Answer:

The Anti-A, Anti-B and Anti-D serums react with the respective antigens on the blood cells to cause agglutination, unless the antigens are absent (as in O negative blood type).

Explanation:

Blood is typed according to the presence or absence of antigens on the blood cells.

The three dominant antigens (surface protein molecules) tested for blood typing are A, B and D. The presence, combination, or absence of the first two determine whether a person is A, B, AB or O, while the presence or absence of the third determines whether a person is Rh positive or Rh negative. See the link for details:

What are the four major blood groups?

For blood typing, three serums are used: Anti-A (which binds with the A-antigen), Anti-B (which binds with the B-antigen) and Anti-D (which binds with the D-antigen).

When blood is tested with these three serums, the presence of any of the three antigens will cause the antibodies in the relevant serum to bind to the cells and cause agglutination.

Thus:
If agglutination is seen only with Anti-A, the blood type is A.

If agglutination is seen only with Anti-B, the blood type is B.

If agglutination is seen with both Anti-A and Anti-B , the blood type is AB.

If agglutination is seen neither with Anti-A nor with Anti-B , the blood type is O.

If agglutination is seen with Anti-D, the blood subtype is Rh positive.

If agglutination is not seen with Anti-D, the blood subtype is Rh negative.