Antibodies against M proteins and their importance in the blood


An M protein is an antibody or part of an antibody that can be found in your blood and / or urine tests, and its presence can mean different things. In blood cancers like myeloma , the "M" in "M protein" stands for monoclonal. Monoclonal protein is produced by abnormal, cancerous, or precancerous cells. It is called a monoclonal protein because there is only one clone, a monoclone of "identical twin cancer cells" that all produce this protein. Protein M is like a mass-produced defective product; it does not fight infection and is useless.

extend01 / iStock

In the picture, the Y-shaped blue antibody or immunoglobulin is M.

The large, round object behind him is a plasma cell that produces antibodies. Not all M proteins are complete antibodies, as shown in the figure. Sometimes myeloma M protein is just one part of an antibody.

Other links to Protein M

In the context of myeloma, the M protein refers to the abnormal production of plasma cells that produce antibodies. Unfortunately, the 'M protein' can have different meanings in medicine, depending on the topic or disease being discussed.

Protein M can also be described using the following terms :

  • Monoclonal protein
  • Myeloma protein
  • Immunoglobulin-free light chains
  • Paraproteins
  • Chipmunks Bens Jones
  • Thorn M
  • Component M

In this article, we mainly talk about the M protein, which is associated with cancer and more specifically with certain types of blood cancers and precancerous conditions of the blood and bone marrow. However, there are some other notable M proteins found in medicine, especially in relation to infectious pathogens, as shown here:

  • The M protein can denote a viral matrix protein, as well as the influenza virus M1 protein.
  • The M protein can be used to refer to a specific bacterium Streptococcus pyogenes.
  • The M protein, or actually "M protein", is related to the bacterium Mycoplasma genitalia .

Blood cancer

The proteins of whole antibodies are called immunoglobulins. Protein M is an immunoglobulin or part of an immunoglobulin that is described as monoclonal, meaning that it is produced by a clone of problem cells. It is not normal for the body to have as many copies of the same protein as it usually has with myeloma, and this excess is found in laboratory studies. It can also cause problems in the body, especially if the levels are too high.

Where he came from

In multiple myeloma, the M protein comes from a large number of plasma cells. Plasma cells usually produce a wide variety of antibodies. In a normal or healthy state, a population of plasma cells is capable of producing a wide range of different antibodies, so-called polyclonal antibodies or polyclonal immunoglobulins. When plasma cells turn cancerous, a very bad cell often arises, giving rise to many of the same henchmen. All minions are clones of the same cell and only produce the same monoclonal proteins. Since there are many plasma cells that multiply abnormally, they produce a large amount of this monoclonal protein. The abundance or burst in volume of a single protein can be determined in laboratory tests .

The structure of monoclonal antibodies.

Each antibody has four parts. Inside there are two long chains and outside two shorter ones. In the picture, you can see a plasma cell with an antibody and many other tiny antibodies in the background.

The light chains or shorter outer lines in the blue Y in the figure are also called Bence Jones proteins or immunoglobulin free light chains . In this case, it is just a small part of a large antibody. When M protein is a light chain, it is actually small enough to pass through the kidneys into the urine. So if you only do a blood test, you can skip the light chains as they entered the urine.

On the other hand, if the M protein is a complete immunoglobulin, all of the large Y in the picture, then it can be found in the blood because it is too large to pass into the urine. And because these large proteins are retained, excessive buildup of M protein in the kidneys can cause kidney disease.


  • Diagnosis: M protein is often found in multiple myeloma and several other conditions .
  • Kidney damage: When M proteins are large enough and in sufficient quantities in the case of a malignancy to block the functional units of the kidneys, this can lead to kidney disease and ultimately kidney failure.
  • Other deleterious effects are possible depending on the characteristics of the secreted protein.

Blood and bone marrow status high in M protein

Conditions that can lead to an increase in M protein levels in urinalysis include :

  • Myeloma: A urine test will be positive for M protein in 50-80% of people with myeloma.
  • MGUS: Monoclonal gammopathy of undetermined significance may be elevated.
  • Waldenstrom's macroglobulinemia : This cancer that affects the precursor cells of plasma cells may have elevated levels of M protein.

In some cases, the cells that cause M protein are cancerous and can affect the bone, lymph nodes, liver, spleen, or other organs. This occurs in multiple myeloma, solitary plasmacytoma, and Waldenstrom's macroglobulinemia.

In other cases, the M protein is produced by a small, limited, precancerous cell clone that has grown, and this does not cause any symptoms. This is a case of monoclonal gammopathy of undetermined significance, MGUS.

Get the word of drug information

Many conditions can cause monoclonal gammopathy, the release of a single protein product; And not all of these conditions are cancerous. You may have M protein in certain connective tissue conditions, such as systemic lupus erythematosus, rheumatoid arthritis, and psoriatic arthritis. You can get it if you get the hepatitis C virus and HIV / AIDS. It can even be with acquired von Willebrand disease, a rare bleeding disorder. Thus, in many cases, the reason for the appearance of the M protein is more important than the mere presence of this discovery.

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