A monoclonal protein, also referred to as M-protein, is an immunoglobulin found in the blood serum or urine, as stated by the Helen Diller Family Comprehensive Cancer Center of the University of California. Monoclonal proteins proliferate from a single clone of plasma cells that share genetic characteristics with myeloma cells. Although typically non-cancerous, increased levels of M-proteins can progress into multiple myeloma, amyloidosis or lymphoma, according to the American Cancer Society.
Lymph cells are white blood cells that produce an immune response when the body encounters foreign invaders. These cells are categorized into two major groups: B cells and T cells. Differentiated B cells transform into plasma cells that are predominantly located in the bone marrow.
Plasma cells produce antibodies called immunoglobulins, to combat antigens. Immunoglobulins are protein complexes composed of two light chains linked to two heavy chains. Light chains can be kappa, lambda or gamma. Heavy chains are classified into five types: IgG, IgA, IgD, IgM and IgE. When aberrant plasma cells replicate multiple copies of only one type of antibody, the antibody is referred to as a monoclonal protein. Commonly produced monoclonal proteins in the bone marrow include IgG kappa, IgG lambda, IgA kappa, IgA lambda or IgA gamma, based on a clinical presentation by the National Cancer Institute.
Monoclonal proteins are usually associated with monoclonal gammopathy of undetermined significance, or MGUS. They are generally detected as incidental findings during blood tests. Most people with MGUS do not require medical treatment.
In the majority of cases, MGUS is not harmful and carries no side effects. Too much accumulation, however, may cause damage to other body tissues and progress to other disorders, including blood cancer, cites Mayo Clinic.
Those testing positive for M protein are encouraged to schedule periodic checkups to monitor protein levels; in most instances, no further treatment is required.