Precipitation occurs with most antigens because the antigen is multivalent i,e., has several antigenic determinants per molecule to which antibodies can bind. Antibodies have at least two antigen binding sites, thus large aggregates or lattices of antigen and antibody are formed. Experimentally, an increasing amount of antigen is added to a constant amount of antibody in solution, initially at low antigen concentration, all of the antigen is contained in the precipitate. this is called the antibody-excess zone (Prozone phenomenon). As more antigen is added, the amount protein precipitated increases until the antigen/antibody molecules are at an optimal ratio. This is known as the equivalence zone or equivalence point. When the amount of antigen in solution exceeds the amount of antibody, the amount of precipitation will decrease. This is known as the antigen excess zone.
The line will give a full identity (continuous line), partial identity (continuous line with a spur coming off one end - like a branch off the main line) or a non identity where the two lines cross completely.
The type of line will tell us that the patient does have some form of antibody likely to be associated with a connective tissue disease.
Comparison of the Sensitivity of 2 Automated Immunoassays with Immunofixation Electrophoresis for Detecting Urine Bence Jones Proteins
Aug 01, 2005; Bence Jones proteins [monoclonal free immunoglobulin light chains (FLCs)] are important tumor markers for identifying and...