Coombs sera & agglutination potentiators
Reagents for the (in)direct antiglobulin test (Coombs sera)
Anti-human globulin (AHG) contains antibodies against human IgG. These antibodies bind to the IgG-molecules on the erythrocytes. This forms a bridge and the erythrocytes agglutinate. Most allo-antibodies directed against erythrocytes are IgG-antibodies.
The large majority of IgG-antibodies is not complement binding. However, there are examples of antibodies that could only be detected indirectly with anti-complement. Therefore, the composition and quality of the AHG reagents are important.
Polyspecific AHG reagent
Polyspecific AHG reagent is mainly used in the antiglobulin test in saline, albumin or LISS. In the PEG and polybrene technique always a-IgG is used. It contains only anti-IgG (monospecific anti-human globulin reagent). Anti-complement in these techniques practically always results in false positive results.
The PEG technique is very sensitive. Antibodies, that can be detected in other techniques only because of their complement activating capacity (like anti-Jka and anti-Jkb), can be detected in the PEG-IAT without the use of an anti-complement.
Agglutination potentiating reagents
The effect of agglutination enhancers is a reduction of the water mantle and ion cloud around the erythrocyte or an increase in the interaction between antigen and antibody.
Agglutination enhancers can influence the zeta potential so that incomplete antibodies can agglutinate red cells and can increase the binding (association) between antibody and antigen.