The specificity of an antibody for a given antigen is characterised by the crossreactivity. Crossreactivity describes the structural relationship between the antigen and the binding domain on the antibody. An antibody is classified as highly specific when it binds exclusively with one defined antigen. In practice, the ideal antibody with one hundred per cent specificity does not exist. Every antibody, to a certain degree, also recognises antigens with structural homology (Fig. 22.6).
A high degree of crossreactivity of the antibody will inevitably result in interference in the immunoassay.
