Bence Jones Proteins - Definition, Biology, and Importance

What Does it Mean to Have Bence Jones Proteins in Your Urine?

What are Bence Jones proteins and why are they important?. Istockphoto.com/Stock Photo©Svisio

Definition: Bence Jones Proteins

Bence Jones proteins are the "light chain" portion of immunoglobulin protein (part of an antibody) excreted in the urine of myeloma patients.

Bence Jones proteins may also be called myeloma protein, M-proteins, paraproteins, free immunoglobulin light chains, or an M-spike.

Conditions in Which Bence Jones Proteins May be Present

There are several conditions in which Bence Jones proteins may be found in a person's urine.

  These include:

  • Multiple myeloma - Multiple myeloma is a blood cancer in which there is an overproduction of plasma cells - cells that develop from B lymphocytes in the bone marrow.  Plasma cells are the cells that make antibodies which protect us from viruses and bacteria.  Between 50 and 80% of people with myeloma will have a urine test positive for these proteins.
  • Waldenstrom's macroglobulinemia - Waldenstrom's macroglobulinemia is an uncommon cancer occurring in B lymphocytes (a type of white blood cell) before they turn into plasma cells.
  • MGUS - MGUS stands for monoclonal gammopathy of undetermined significance.  This disease may be a precursor of multiple myeloma and involves an increase in the number of plasma cells, but none of the other symptoms associated with multiple myeloma.

Origin and Significance of Bence Jones Proteins - Where do They Come From?

To understand why Bence Jones proteins may be in your urine, and why that is important, it helps to back up to the first steps in multiple myeloma.

Multiple myeloma is a blood cancer involving the excess production of plasma cells.  Just as a lung cancer would have an excess of abnormal lung cancer cells, myeloma involves an excess of plasma cells.

Plasma cells are the cells which make antibodies to help us fight off disease. Cancerous plasma cells, however, don't make antibodies that help fight off disease, and instead, the excess plasma cells make excess antibodies which are all the same.

When you hear the term "monoclonal" this simply means they are all the same - "one clone."

What is a "Light Chain" Portion of an Immunoglobulin?

Antibodies are what scientists call immunoglobulins - immune meaning they help fight disease, and globulin, meaning they are proteins.  These immunoglobulins are usually quite large, but some portions are smaller.  In the picture above, you can see a full antibody or immunoglobulin, but these are made up of a few parts.  The blue parts are the "heavy chains" and the gold parts are the "light chains."

In this picture, the gold light chains are what we call Bence Jones proteins.

What do Bence Jones Proteins Do?

The excess of immunoglobulins in the body becomes a problem when they break apart.  Ordinarily, these antibodies are too large to be filtered through the tubules in the kidneys.  These light chains - the Bence Jones proteins - however, are small enough to enter the filtering units in the kidneys.  In the kidneys that essentially clog the tubules, leading to kidney damage.

Urine Test for Bence Jones Proteins

The test for Bence Jones proteins involves collecting your urine for 24 hours to check for evidence of the proteins.  Bence Jones proteins are named for Henry Bence Jones, a chemical pathologist who first discovered the unusual properties of these urine samples in the mid-1800s.

Next Steps

If you're newly diagnosed there are a few steps to consider before doing anything.  Take time to learn about your disease and ask questions.  Reach out for support from your friends and loved ones.  And hang on to hope.  The treatment of blood cancers has improved markedly in recent years, and new treatments are currently in clinical trials.

Sources:

Kyle, R., Larson, D., Therneau, T. et al. Clinical course of light chain smoldering multiple myeloma (idiopathic Bence Jones proteinuria): a retrospective cohort study. Lancet Haematology. 2014. 1(1):e28-36.

Continue Reading