Final answer:
Heterophile antibodies can interfere with immunoassays by causing non-specific binding, leading to false-positive results or inaccurate interpretation of the assay titer, especially in diseases like infectious mononucleosis.
Step-by-step explanation:
Heterophile antibodies can interfere with an immunoassay by causing non-specific agglutination or binding, leading to false-positive results. This immunological cross-reactivity occurs because heterophile antibodies have broad specificity and can bind to a variety of antigens, including those used in immunoassays. In the context of infectious mononucleosis (IM), for example, the detection of heterophile antibodies that bind to animal red blood cells is a diagnostic indicator.
However, when they cross-react with assay antigens or with self-antigens, they can compromise the specificity of the assay and generate misleading results. In assays such as hemagglutination inhibition (HAI), they may cause improper interpretation of the titer of virus-specific antibodies by causing agglutination when it should be inhibited, or they might inhibit agglutination unintentionally. This is particularly relevant for diseases like HIV, hepatitis, rubella, or in the presence of autoimmune diseases, which can yield elevated levels of heterophile antibodies and lead to indeterminate results.