Which of the following is commonly involved in multiple myeloma:
**Core Concept**
Multiple myeloma is a type of plasma cell malignancy characterized by the proliferation of clonal plasma cells in the bone marrow. The disease is often associated with genetic abnormalities and aberrant expression of cell surface antigens.
**Why the Correct Answer is Right**
The correct answer involves the Fc receptor for IgG (FcγRII, also known as CD16), which is a key receptor involved in the pathogenesis of multiple myeloma. In multiple myeloma, the malignant plasma cells often express FcγRII, which can lead to an abnormal interaction with the Fc region of IgG antibodies, resulting in enhanced survival and proliferation of the myeloma cells. The interaction between FcγRII and IgG antibodies can also trigger a series of downstream signaling pathways that promote myeloma cell growth and survival.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe a common feature of multiple myeloma. While some myeloma cells may express FcγRIII, this is not the most relevant receptor involved in the pathogenesis of the disease.
**Option B:** This option is incorrect because it is not a characteristic of multiple myeloma. The FcεRI is a high-affinity receptor for IgE, which is primarily involved in allergic reactions and mast cell activation.
**Option C:** This option is incorrect because it is not a receptor commonly associated with multiple myeloma. The FcRn (neonatal Fc receptor) is involved in the transport of IgG antibodies across the placenta and in the recycling of IgG from the neonatal gut.
**Clinical Pearl / High-Yield Fact**
Multiple myeloma cells often express abnormal levels of cell surface antigens, which can lead to an abnormal interaction with the immune system and contribute to the disease's pathogenesis. The FcγRII is a key receptor involved in this process, and its expression can be used as a diagnostic marker for multiple myeloma.
**Correct Answer:** C.