Enhancement Media

The purpose of enhancement media is to increase detection of IgG antibodies, which are often thought to be more clinically-significant since they are optimally reactive at 37°C.

  • RBCs are surrounded by negative charge because of sialic acid on their membranes. This repels other RBCs and prevents RBC adherence to each other in vivo. This zone of negative charge attracts an ionic cloud of positively-charged cations, creating a potential known as the zeta potential. This influences the reactivity of IgM and IgG antibodies.
  • Low ionic strength solution (LISS): generally contains 0.2% saline. This reduces the zeta potential and increases the rate of antibody uptake during sensitisation. However, it may result in false positives and may need to be repeated using albumin.

Proteolytic Enzymes

  • Enzymes modify certain blood group antigens, and are useful in serologic testing. 
  • Enzymes and their sources:
    • Papain (from papaya)
    • Ficin (from fig plants)
    • Trypsin (from pig stomach)
    • Bromelin (from pineapples)
  • Enzymes enhance the reactivity of:
    • Rhesus 
    • Kidd
    • P
    • Lewis
  • Enzymes destroy:
    • Duffy (Fya, Fby)
    • MNS
  • They have no effect on:
    • Kell

Antihuman Globulin (Coombs Reagent)

  • Used to identify antibodies which are coating the red cell surface, but do not directly agglutinate 
  • AHG induces agglutination by binding to the Fc portion of bound antibodies
  • AHG can be polyspecific (IgG and complement), or monospecific (IgG or complement)

ZZAP and DTT

  • Dithiothreitol (DTT) destroys the J (joining) chain of the IgM molecule, destroying it while leaving IgG intact
  • ZZAP is a combination of DTT and proteolytic enzyme
  • These can be used to destroy Kell antigens