Immunofixation

Immunofixation permits the detection and typing of monoclonal antibodies or immunoglobulins in serum or urine. It is of great importance for the diagnosis and monitoring of certain blood related diseases such as myeloma.
Principle.
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 as a function of their specific electrophoretic mobility. For the purpose of 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.
Technique.
The technique consists of depositing a serum (or urine which has been previously concentrated) sample 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 are laid upon the gel. It thus appears to be more or less narrow bands on the gel, which are at different immunoglobulins.
Immunofixation as immunoelectrophoresis, takes place in two steps:
Merits.
Immunofixation tends to replace protein electrophoresis because :
Demerits.
Immunofixation is however only sensitive to immunoglobulins and is more expensive than protein electrophoresis.