Bence Jones proteins are composed of what type of immunological component?

Bence Jones proteins are primarily composed of monoclonal free light chains. These proteins are typically found in the urine of patients with certain types of plasma cell disorders, like multiple myeloma. The abnormal proliferation of plasma cells in such conditions leads to the overproduction of light chains, which can then be detected as Bence Jones proteins.

Unlike monoclonal antibodies, which consist of both heavy and light chains and function in immune response, Bence Jones proteins specifically refer to the free light chains that are not bound to heavy chains. They are called "monoclonal" because they originate from a single clone of plasma cells, hence their uniformity in structure.

Polyclonal antibodies involve the response from multiple B cell clones and are not related to the production of Bence Jones proteins. Similarly, heavy chains of immunoglobulins are part of the complete immunoglobulin molecule and do not form Bence Jones proteins, which lack heavy chains.

Thus, the identification of Bence Jones proteins as monoclonal free light chains is critical in diagnosing and monitoring conditions like multiple myeloma.