Bence Jones proteins are derived from:
**Core Concept**
Bence Jones proteins are abnormal proteins found in the urine of patients with multiple myeloma and other plasma cell dyscrasias. These proteins are light chains of immunoglobulins that are produced by malignant plasma cells.
**Why the Correct Answer is Right**
Bence Jones proteins are specifically derived from the light chains of immunoglobulins (Ig). The light chains are either kappa (κ) or lambda (λ) chains, and they are produced by plasma cells in response to an antigenic stimulus. In multiple myeloma, the malignant plasma cells produce excess amounts of these light chains, which are then excreted into the urine. The presence of Bence Jones proteins in the urine is a diagnostic hallmark of multiple myeloma.
**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because Bence Jones proteins are not derived from the heavy chains of immunoglobulins. The heavy chains (μ, δ, γ, α, and ε) are also produced by plasma cells, but they do not form the basis of Bence Jones proteins.
* **Option B:** This is incorrect because Bence Jones proteins are not derived from the complement system. While the complement system is an important part of the immune response, it is not directly involved in the production of Bence Jones proteins.
**Clinical Pearl / High-Yield Fact**
Bence Jones proteins are a classic example of a paraprotein, which is an abnormal protein produced by a clone of malignant plasma cells. The presence of paraproteins in the urine or serum is a diagnostic clue to the presence of a plasma cell dyscrasia, such as multiple myeloma.
**Correct Answer:** C. Light chains of immunoglobulins.