Question

If a person has alloantibody that cannot be identify, would it be sent it out? If so, what techniques would the reference laboratory use to identify it?

Answer 1

Alloantibodies are antibodies that are against other blood groups (not A and B). They are found in 0-3-2% population. Alloantibodies can be generated due to previous blood transfusion or pregnancy. Alloantibodies include anti-E, anti-Le(a), anti-K, anti-D, and anti-Le(b) [11]. However, it is clinically important only if this alloantibody causes a hemolytic transfusion reaction or hemolytic disease of the newborn. Clinically important alloantibodies include ABO (A, B), Rh (D, C, c, E, e), Duffy (Fya, Fyb), Kidd (Jka, Jkb), Kell (K, k), SsU (S, s, U), and Lutheran (Lub).

Single alloantibodies are easy to identify if it yields clear-cut positive and negative reaction with RBC samples. The strength of observed reactions varies due to dosage affect, variation in antigen amounts, deterioration during storage or the presence of multiple antibodies.

When an alloantibody cannot be identified, samples are sent to immunohaematology reference laboratories that have the necessary rare cells to study the alloantibody. These tests include:

Enzyme techniques: Treatment of RBCs with proteolytic enzymes increases the reactivity of complement binding alloantibodies such as anti-Jka. These techniques are used when a weakly reactive antibody may be an Rh or Fey antibody.

Temperature reduction, altering pH and increasing the incubation temperature: This technique can be used to for antibodies such as anti-M, anti-P that react better in cold temperature. Altering the condition will allow better reactivity. These tests include low-ionic-strength saline solution (LISS) or PEG ant globulin test. LISS reagent accelerate first stage of antigen-antibody reaction as it decreases the ionic strength

ZZAP contains cysteine-activated proteolytic papa in and dithiothreitol (DTT). It is enhances the dissociation of red cell bound IgG by causing loss of integrity of IgG molecules. Hence, antibodies that are underlying can be detected.

Thiol containing Reagent Test: Dithiothreitol (DTT) and 2-mercaptoethanol (2-ME) cleaves inter-subunit disulphide bridges between IgM antibodies but not IgG molecules. Hence, IgG molecules can be detected, as IgM will be destroyed.

Prewarm antibody screen: The serum is added to prewarmed RBCs before the antihaemaglutinin test is performed. This allows the detection of cold auto-agglutinin or underlying alloantibodies.

Lewis, P¹ and Sid substance: Lewis substance ^Lea and Le^b are present in saliva of people with Lewis phenotype. If present, it will neutralize the Lewis antibody. Soluble P substance is present in hydatid cyst fluid and can mask presence of alloantibody. This substance is removed by agglutination with specific antibody, allowing the detecting of alloantibody. Sd_a is present in present in many body fluids as soluble form. It is removed using specific antibody, which allows detection of underlying alloantibody.