Blood donations

Can anyone help me with a few questions please?
-What exactly are 'agglutinins'? Are they the antibodies?
-Apparently O can donate to anyone, but O has Antibody A and B, so if they donate to A, the antibody A will react with antigen A won't it? and vice versa... Thanks

Reply 1

futuredoctorVSB

Original post by Qaiys

Agglutinins are kind of like surface proteins, on red blood cells. Antibodies can bind to these surface proteins and cause clotting and immune responses etc.

There are two main agglutinins: A and B

In blood Group A, the red blood cells have an A agglutinin, and the blood has the anti b antibody. (Can only get from A and O)

In Blood Group B, the red blood cells have a B agglutinin and the blood has the anti a antibody. (Can only get from B and O)

In blood Group AB, the red blood cells have both the a and b agglutinins, but their blood has no agglutinin-binding-antibodies (Can receive from any group)

In people with Blood Group O, their RBCs don't have any agglutinins, but their blood has both Anti A and Anti B antibodies. (Can donate to any group, but can only get blood from O)

Reply 2

white_o

Original post by futuredoctorVSB

But if O has Anti A and Anti B, won't they react with the Antigen A or Antigen B in A and B groups?

Reply 3

Dynamo123

Original post by Qaiys

But if O has Anti A and Anti B, won't they react with the Antigen A or Antigen B in A and B groups?

The amount of blood transfused is normally not high. When this blood group O, containing, as you say, anti A and anti B antibodies, is injected or transfused, it is greatly diluted when it mixes with the huge blood in your circulation. Therefore this effect is too weak to be of any significant nature.

Reply 4

white_o

Original post by Dynamo123

So then why can't any blood be donated to any other type if the effects are so weak?

Reply 5

Revenged

Original post by Dynamo123

This is not true.

The reason is because blood is separated into components because it is spun very fast in the centrifuge (spin machine).

The haematocrit contains the red blood cells and is separated from the plasma that contains antibodies.

In real life there is some antibodies left so we always give patients blood of exactly the same blood type. Only in an emergency do you give O negative blood.

(There is another group called resus group which is why blood is called positive or negative)

(edited 9 years ago)

Reply 6

Dynamo123

Original post by Revenged

Well, my textbook on Physiology (Guyton's TMP) says that:
"It is rare that the transfused blood causes agglutination of the recipient’s cells, for the following reason: The plasma portion of the donor blood immediately becomes diluted by all the plasma of the recipient, thereby decreasing the titer of the infused agglutinins to a level usually too low to cause agglutination. Conversely, the small amount of infused blood does not significantly dilute the agglutinins in the recipient’s plasma. Therefore, the recipient’s agglutinins can still agglutinate the mismatched donor cells."
While I think that this is the case, your point is equally valid: blood is centrifuged and separated into plasma and blood cells, and then we choose which portion the recipient requires.
Cheers :biggrin: