IgG4 is a unique antibody. Firstly distinguished by it’s small size compared to IgG1-3, and by it’s higher level of disulfide bonds. It also has its own distinct activity.
IgG4 is important in relation to IgE because it can act as a blocking agent for an IgE reaction, reducing anaphylaxis and the symptoms mediated by IgE, although, if too high it can also result in a secondary set of conditions of its own.
When the IgG4 reaction is greater than the IgE reaction for a particular antigen, IgG4 can block the IgE antibodies from binding to the receptor sites that would encourage the release of histamine, thereby reducing severity of the symptoms associated with the IgE reaction. This is referred to as the ‘blocking potential’, which is displayed on the report.