What causes a prozone reaction?

A prozone reaction occurs when there is an excess of antibody relative to the amount of antigen present in a sample. This imbalance leads to incomplete antigen-antibody complex formation, which can result in a false negative or weak positive result in serological tests. Specifically, in the context of immunological assays, if too much antibody is present, it may saturate the available antigen sites, preventing effective cross-linking and visible precipitation from forming.

In serological testing, it is crucial to maintain a balanced ratio of antigen and antibody to achieve optimal results. Antigen excess or a balanced ratio generally does not lead to a prozone effect, while inadequate temperature primarily affects the functionality and binding of the antibodies and antigens rather than causing this specific reaction. Thus, the presence of excess antibodies is the key factor that directly leads to the prozone phenomenon.