The method detects by precipitation: when a soluble antigen (Ag) is brought in contact with the corresponding antibody, precipitation occurs, which may be visible with the naked eye or microscope.
Immunofixation identifies (antibodies) in a mixture in function of their specific electrophoretic mobility. For the identification antigens are used that are specific for the targeted antibody.
Specifically, immunofixation allows the detection of monoclonal antibodies representative of diseases such as myeloma or Waldenström macroglobulinemia.
It consists in depositing the serum (or urine which has been previously concentrated in) on a gel. After application of an electric current that allows the separation of proteins according to their size, antibodies specific for each type of immunoglobulin were laid upon the gel. It thus appears the more or less narrow bands on the gel, which are at different immunoglobulins.
Immunofixation as immunoelectrophoresis, takes place in two steps:
The first step is identical for both techniques. It consists in depositing the immunoglobulins contained in the serum or urine on a gel and then separating the immunoglobulins according to their electrophoretic mobility by making migrate under the effect of an electric field. This migration depends on the mass and charge of the antigen. Once separated immunoglobulins, we can move to the next step.
The second step is based on the technique used. Immunofixation requires to migrate serum tested several times. For this anti-immunoglobulin are not placed in a channel, as in electrophoresis, but they are added individually to each migration lane. The presence of a monoclonal immunoglobulin results in the appearance of a narrow band after staining complex precipitates. For example, in the case of an IgG lambda, there will be a narrow band, both on the track on which was deposited anti-G and on which has been deposited that the anti-lambda.