Immunofixation permits the detection and typing of

monoclonal antibodies A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a cell Lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell. Monoclonal antibodies ca ...

or immunoglobulins in serum or

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...

. It is of great importance for the diagnosis and monitoring of certain blood related diseases such as

myeloma Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibodies. Often, no symptoms are noticed initially. As it progresses, bone pain, anemi ...

Principle

The method detects by

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

: when a soluble

antigen In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

(Ag) is brought in contact with the corresponding

antibody An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

, precipitation occurs, which may be visible with the naked eye or microscope. Immunofixation first separates

antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

in a mixture as a function of their specific

electrophoretic Electrophoresis, from Ancient Greek ἤλεκτρον (ḗlektron, "amber") and φόρησις (phórēsis, "the act of bearing"), is the motion of dispersed particles relative to a fluid under the influence of a spatially uniform electric fie ...

mobility. For the purpose of identification, antisera are used that are specific for the targeted antibodies. 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 Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

according to their size, antibodies specific for each type of

immunoglobulin An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

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: * 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 them migrate under the effect of an electric field. This migration depends on the mass and charge of the antigen. Once the immunoglobulins are separated, we can move to the next step. * The second step is based on the technique used. Immunofixation requires electrophoresis to migrate serum proteins in replicate. Then, specific anti-immunoglobulin antisera are used to treat each replicate. For this, the antisera 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 with the anti-lambda.

Merits

Immunofixation tends to replace

protein electrophoresis Protein electrophoresis is a method for analysing the proteins in a fluid or an extract. The electrophoresis may be performed with a small volume of sample in a number of alternative ways with or without a supporting medium: SDS polyacrylamide gel ...

because : * it is faster (results within three hours) ; * it is somewhat more sensitive. Immunofixation may reveal an immunoglobulin missed out by protein electrophoresis, especially at low concentrations (less than 1 gram/litre) ; * it can be partially automated and can be used in more laboratories; * it is more easily read and interpreted.

Demerits

Immunofixation is however only sensitive to immunoglobulins and is more expensive than protein electrophoresis.

References

Sources

* :fr:Immunofixation

External links

* - "Immunofixation - serum" * - "Immunofixation - urine" {{Immune_proteins Glycoproteins Immunologic tests