IMMUNOFIXATION-BENCE JONES IDENTIFICATION

CLINICAL UTILITY:

Detecting the presence of monoclonal immunoglobulins or fragments of immunoglobulins in serum or urine is important in the diagnosis and management of a variety of B-cell malignancies. Most frequently associated with these monoclonal or +‘M components+’ are multiple myeloma, Waldenstrom’s macroglobulinemia, lymphomas and chronic lymphocytic leukemia. Autoimmune diseases such as SLE and Sjogren’s syndrome are other conditions in which monoclonal components may occur.

In monoclonal gammopathy of uncertain significance (+‘MGUS+’), which also may be referred to as +‘benign monoclonal gammopathy+’, relatively small concentrations of M-components are present in the serum or urine without other clinical significance. Monoclonal proteins have been found in 5% of all persons over the age of 50, and in 8% over the age of 70. A few of these people eventually will develop multiple myeloma or other B-cell neoplasms, and others may develop amyloidosis.

Frequently appearing in the urine of patients with paraprotein diseases are Bence Jones proteins, which are monoclonal light chain fragments of immunoglobulins (either kappa or lambda light chains). Occasionally, free monoclonal light chains also are detected in serum.

In multiple myeloma most patients (80%) have a serum paraprotein, and about half have a urinary (Bence Jones) paraprotein. The most common class of monoclonal component found in this disease is IgG (about 50%), with about 25% IgA. About 20% of patients have only Bence Jones protein, with little or no serum monoclonal component. In rare cases, the M component is IgD.

High serum levels of IgM occur in Waldenstrom’s macroglobulinemia, frequently causing hyperviscosity syndrome. Bence Jones proteinuria is found in about 10% of these patients. Most patients with amyloidosis of the light-chain (AL) type also have Bence Jones protein.

Immunofixation is a sensitive follow-up method used to determine the class and clonality of serum or urine proteins which are suspected of being monoclonal (paraproteins). M components appear as narrow bands, spikes or restrictions on protein electrophoresis, and can be identified specifically by immunofixation. In some cases of hypergammaglobulinemia associated with inflammation, serum electrophoresis reveals bands in the gamma region which are shown by immunofixation to be polyclonal or oligoclonal.

METHOD DESCRIPTION:

Immunofixation is the method used to identify monoclonal proteins in both serum and urine. Following high resolution agarose electrophoresis, the gel is incubated with specific anti-sera to detect each of the immunoglobulins (heavy chains and light chains). The gel is then dried and stained before interpretation.

REFERENCE RANGE:

No monoclonal component (serum); No Bence Jones Protein (urine).

SPECIMEN REQUIREMENTS:

Serum: 0.5 ml serum
Urine: 25.0 ml urine