M Protein

**Semantic type:** Amino Acid, Peptide, or Protein|Immunologic Factor

**Definition:** A protein complex comprised of two heavy chains and two light chains. Monoclonal immunoglobulin (M protein) is found in abundance in patients who have multiple myeloma. The protein is not produced in response to an antigen, but it is expressed in malignant plasma cells and excreted into the blood and urine.

**Synonyms:** - M Component - M Proteins - M protein - M-Protein - Monoclonal immunoglobulin - Myeloma Protein - Paraprotein - Spike Protein - monoclonal protein