TTG and Anti-Tissue Transglutaminase: Clarification of Terminology
TTG and anti-tissue transglutaminase refer to different entities: TTG (or tTG) is the abbreviation for tissue transglutaminase, which is an enzyme protein in the body, while anti-tissue transglutaminase (anti-tTG) refers to the antibodies directed against this enzyme that are measured in celiac disease testing. 1
Understanding the Distinction
Tissue Transglutaminase (tTG) - The Antigen
- tTG is an enzyme that can bind and hydrolyze GTP and function as a protein crosslinking enzyme, widely expressed both inside cells and in the extracellular space 2
- This enzyme is the main autoantigen recognized by endomysial antibodies in celiac disease 3, 4
- tTG exists in different conformational states (open and closed) that affect its biological activity 2
Anti-Tissue Transglutaminase (anti-tTG) - The Antibody
- Anti-tTG antibodies are the immune response produced against the tissue transglutaminase enzyme 1
- These antibodies are specifically produced in the small-intestinal mucosa of celiac disease patients and serve as diagnostic markers 5
- The antibodies are measured as IgA or IgG isotypes (anti-tTG IgA or anti-tTG IgG) in serologic testing 1
Clinical Context and Usage
In Medical Documentation
- When guidelines reference "tTG" in abbreviation lists, they typically mean "anti-tissue transglutaminase" in the context of serologic testing 1
- The full term clarifies whether discussing the enzyme itself or the antibodies against it 1
Diagnostic Testing
- Anti-tTG IgA is the primary screening test for celiac disease with sensitivity of 90.7% and specificity of 87.4% in adults at threshold of 15 U/mL 6
- The test measures antibodies in the patient's blood, not the enzyme itself 1, 7
- Testing should be performed while the patient is on a gluten-containing diet to avoid false negative results 6, 8
Common Clinical Pitfall
The abbreviation "tTG" in clinical practice almost always refers to the antibody test (anti-tTG), not the enzyme itself, though technically tTG is the enzyme and anti-tTG is the antibody. 1 This shorthand is widely accepted in medical communication, but understanding the distinction is important when interpreting pathophysiology, as the antibodies act on the enzyme to trigger cellular responses in celiac disease. 5