2. Elution
The word elute is used to define the removal or extraction of a material from another.
Elution typically involves removing an adsorbed material using a solvent.
Elution at blood banks is done to remove antibodies from the surface of red blood
cells, identify complex antibodies
3. Adsorption
• Adsorption is serologic testing method used to separate antibodies from serum
in order to appropriately identify underlying alloantibodies
• Antibodies can be strategically removed from the serum by allowing them to
adsorb onto the surface of red blood cells (RBCs) that express the target antigen
• Adsorbed serum can then be tested for remaining alloantibody reactivity
16. ELUTION- APPLICATIONS
1. Investigation of HDN: an elution is done on the infant's red cells, and the
resulting eluate is tested for the presence of the mother's IgG antibody
which has crossed the placenta and sensitized fetal cells.
2. Investigation of IAHA (warm, cold, and drug-related types): an elution is
done on the patient's red cells and the resulting eluate is tested for
autoantibody specificity.
17. 3. Investigation of hemolytic transfusion reactions: an elution is done on
the patient's post-transfusion red cells, and the resulting eluate tested for
antibody specificity. Note that in this case, even though the antibody elutes
from the patient's red cells, it is not an autoantibody as it actually eluted
from the donor's red cells now in the patient's circulation.
4. Separation of multiple antibodies to aid identification.
5. Confirmation of antibody specificity.
28. This occurs because in PCH, also called Donath Landsteiner’s
hemolytic anemia, the autoantibody binds to the red cells only at low
temperatures and causes complement fixation which leads to
intravascular lysis of RBCs and gives positive result at low
temperatures.
29. ADSORPTION- APPLICATIONS
1. Removing autoantibody activity to permit detection of possible
coexisting alloantibodies. For example, if a patient has an autoanti-1, an
autoadsorption at 4°C can be done to remove it, and the auto adsorbed
serum can be run against a panel to identify any possible alloantibodies
present.
2. Reagent preparation: removing anti-A or anti-B or other unwanted
antibodies from serum that contains an antibody suitable for reagent use,
e.g., serum from a group A donor containing anti-D can be adsorbed with
group B Rh(D) negative blood cells: the anti-B will be adsorbed, but the
anti-D will not.
30. Separating multiple antibodies to aid in identification: for example, if
you suspect a serum contains anti-c and other unidentified antibodies that
react with R1R1 cells, you could adsorb the serum with R1R1 cells. Anti-c
would remain free in the supernatant and could be confirmed by testing the
supernatant with panel cells. The antibodies which attached to the
R1R1 cells could be eluted and identified.
31. 4. Confirmation of the presence of a weak antigen on red cells: this
can be done by proving their ability to adsorb and remove specific
antibody. For example, supposing a patient's ABO group gave the
following results:
The patient may be a group A with a very weak A antigen (weak
subgroup of A). His red cells could be incubated with anti-A at 4°C for
an increased time (e.g., 4 - 12 hours) and then an elution could be
prepared. If the eluate contain anti-A, it is possible to conclude the A
antigen must have been on the red cells.
32. 5. Confirmation of antibody specificity: if you suspect a serum
contains an antibody (e.g., anti-c) plus one or more antibodies (e.g.,
anti-K and anti-Fya), you can confirm the anti-c by doing an adsorption
followed by an elution, e.g., incubate serum with red cells that are Fya-,
K-, but c positive, then do an elution of the adsorbed cells and test it
with panel cells to confirm it contains anti-c.
