Molecular basis of celiac disease

Area of Science:

• Immunology
• Gastroenterology
• Genetics

Background:

• Celiac disease (CD) is a complex intestinal disorder influenced by genetics, gluten exposure, and environmental factors.
• CD4(+) T cells play a crucial role in the immune response to gluten, but the precise mechanisms of tissue damage are not fully understood.
• Understanding CD offers insights into HLA-associated diseases and oral tolerance.

Purpose of the Study:

• To elucidate the mechanisms of immune response and tissue damage in celiac disease.
• To investigate the role of HLA molecules, gluten peptides, and tissue transglutaminase (tTG) in celiac disease pathogenesis.
• To explain the development of gluten-dependent autoantibodies against tTG.

Main Methods:

• Isolation and characterization of gluten-reactive T cells from small intestinal biopsies of celiac patients.
• Analysis of HLA-DQ2 and HLA-DQ8 restriction elements for T cell recognition of gluten peptides.
• Investigation of the role of tissue transglutaminase (tTG) in gluten peptide deamidation and complex formation.

Main Results:

• Gluten-reactive T cells were isolated from celiac patients but not controls, predominantly recognizing deamidated gluten peptides.
• HLA-DQ2 and HLA-DQ8 molecules preferentially bind deamidated gluten epitopes.
• Tissue transglutaminase (tTG) deamidates gluten peptides in vivo, forming gluten-tTG complexes that may induce intramolecular help, leading to tTG autoantibodies.

Conclusions:

• The interaction between deamidated gluten peptides, HLA-DQ2/DQ8, and T cells is central to celiac disease immunopathology.
• Tissue transglutaminase (tTG) plays a key role in modifying gluten and potentially driving autoimmunity through gluten-tTG complex formation.
• These mechanisms explain the characteristic autoantibody response observed in active celiac disease.