What does a monoclonal band identified by immunofixation electrophoresis indicate?

A monoclonal band identified by immunofixation electrophoresis indicates the presence of a specific monoclonal immunoglobulin. This phenomenon occurs when a single clone of plasma cells produces an abundance of identical immunoglobulin molecules, leading to a distinct band that can be visualized on the electrophoresis gel. This is often associated with conditions such as multiple myeloma or certain types of lymphomas, where a single type of plasma cell proliferates.

In contrast, normal plasma cells produce a diverse range of immunoglobulins, which would not create a distinct band. Similarly, polyclonal antibody responses involve multiple clones producing a variety of antibodies, leading to a broad, diffuse pattern rather than a specific band. The presence of fluid overload is unrelated to the identification of monoclonal bands, as it pertains more to volume status rather than immunoglobulin production. Hence, the identification of a monoclonal band specifically points to a single, dominant immunoglobulin produced by a clone of plasma cells.