Cold Agglutinin

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

**Definition:** An autoantibody against a red blood cell surface antigen that causes the cells to clump when the blood is cooled below the normal body temperature (the clumping is most pronounced at temperatures below 78 degrees). Presence of cold agglutinins may be indicative of mycoplasmal pneumonia, mononucleosis, mumps, measles, scarlet fever, some parasitic infections, cirrhosis of the liver, and some types of hemolytic anemia.