Lambda Light Chain: Definition

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A lambda light chain is one of the two types of light chains, a small piece that forms part of every antibody. Antibodies, also called immunoglobulins, are proteins made by B cells and plasma cells to fight infection. Each antibody contains either two lambda light chains or two kappa light chains, never a mix. Pathologists test for lambda and kappa light chains to find out whether a group of B cells or plasma cells is normal or abnormal.

Lambda light chain is a test result, not a diagnosis. This article explains what lambda light chains are, how pathologists test for them, and what a “lambda-restricted” result means in your pathology report.

What are lambda light chains?

Every antibody has four protein chains. Two are larger, called heavy chains, and two are smaller, called light chains. There are two types of light chains, lambda and kappa. Each B cell or plasma cell chooses one type as it develops and makes only that type for the rest of its life.

In a healthy person, the body contains millions of different B cells and plasma cells. Some make lambda light chains,s and some make kappa light chains, so a normal sample contains a mix of both. Normally, there are more kappa-producing cells than lambda-producing cells, usually about two to one.

How do pathologists test for lambda light chains?

Pathologists test for lambda and kappa light chains together so they can compare the results. The tests include:

In situ hybridization. In situ hybridization (ISH) detects the genetic message for each light chain inside the cells on a glass slide. It is especially good at showing light chains in plasma cells.
Immunohistochemistry. Immunohistochemistry (IHC) uses antibodies to detect each light chain protein in tissue.
Flow cytometry. Flow cytometry measures light chains on cells in a liquid sample, such as blood or bone marrow.

Light chains can also be measured in the blood and urine. A blood test called the serum free light chain test measures the amount of lambda and kappa light chains and their ratio

What does a lambda-restricted result mean?

Sometimes almost all of the B cells or plasma cells in a sample make lambda light chains, and very few make kappa. This result is described as “lambda-restricted” or “lambda light chain restriction.” This means the cells most likely came from a single abnormal cell that has multiplied. A group of cells that all came from one cell is called monoclonal or clonal.

A lambda-restricted result supports a diagnosis of a tumor made of B cells or plasma cells. Examples include multiple myeloma, plasmacytoma, monoclonal gammopathy of undetermined significance (MGUS), and many B-cell lymphomas. Light chain restriction alone does not tell the pathologist which condition is present.

What does a mixed result mean?

When the sample contains a mix of lambda-producing and kappa-producing cells in roughly the normal proportion, the result is described as “polytypic” or “polyclonal.” This pattern is seen in normal tissue and in reactions to infection or inflammation. It makes a B-cell or plasma cell tumor less likely, although a small abnormal group can sometimes be hidden among many normal cells.

Are lambda-restricted tumors different from kappa-restricted tumors?

Both lambda-restricted and kappa-restricted results point to the same groups of diseases, and in most conditions the light-chain type does not change treatment. One important exception is amyloid. In AL amyloidosis, light chains made by abnormal plasma cells fold into an abnormal shape and build up in organs. Lambda light chains cause most cases of AL amyloidosis.

Lambda light chains made in large amounts can also pass into the urine, where they are called Bence Jones protein, and can damage the kidneys. Your doctor may order urine or blood tests to look for these effects.

Questions to ask your doctor

Were lambda and kappa light chains tested on my sample?
Was the result lambda-restricted, kappa-restricted, or mixed?
Does the result show a group of abnormal cells?
What is the final diagnosis in my report?
Do I need a serum free light chain test or other blood tests?
Do I need a bone marrow biopsy?
What follow-up do I need?