Which protein class primarily composes the α2-fraction in serum protein electrophoresis?

The α2-fraction in serum protein electrophoresis is primarily composed of haptoglobin. Haptoglobin is an acute-phase protein that binds free hemoglobin released from erythrocytes, which helps to prevent kidney damage and reduce iron loss. During inflammation or tissue damage, haptoglobin levels typically increase as part of the body's response, making it a significant component of the α2-fraction.

While other proteins like transferrin and α1-antitrypsin are important serum proteins, they are primarily localized in other fractions of the electrophoresis pattern. Transferrin, for example, is typically found in the β-fraction, where it functions in iron transport, while α1-antitrypsin belongs to the α1-fraction and serves as a serine protease inhibitor. IgG is a type of immunoglobulin and is mainly present in the γ-fraction of serum proteins, primarily responsible for the immune response. This distinction reinforces the unique roles and placements of these proteins within serum protein electrophoresis.