HLA DQ2 Antigen - An Overview

Introduction to Celiac Disease (CD)

• Celiac disease is an autoimmune disorder triggered by gluten ingestion.
• CD is often linked with genetic predispositions, particularly HLA-DQ2 and HLA-DQ8 haplotypes.
• Common symptoms include intestinal disorders, malabsorption, diarrhea, fatigue, anemia, and various extra-intestinal symptoms.

Role of HLA-DQ2 in CD

• Over 98% of CD patients carry DQ2 or DQ8 HLA class II alleles.
• HLA-DQ2/DQ8 predispose individuals to CD by influencing immune response to gluten.
• HLA-DQ2 homozygosity increases risk of developing CD.

Genetic Aspects

• HLA-DQ molecules are heterodimers composed of alpha and beta chains.
• Gene dose effect: Homozygous individuals for HLA-DQ2 are more susceptible to CD.
• HLA-DQ2 expression influences the immune response strength to gluten.

Immune Mechanisms

• The enzyme tissue transglutaminase (tTG) modifies gliadin, enhancing its binding to HLA-DQ2/DQ8.
• This binding triggers adaptive immune responses, leading to inflammation and autoantibody production.
• Autoantibodies like anti-tTG and anti-gliadin are markers for CD.

Diagnostic and Screening Tests

• HLA-DQ2/DQ8 genetic tests are useful for CD screening.
• Antibody tests (TTG IgA, antiendomysial, antigliadin) help in diagnosis.
• Intestinal biopsy confirms diagnosis through histopathological changes.

Treatment and Management

• Gluten-free diet is the primary treatment.
• Monitoring involves checking antibody levels and nutritional deficiencies.
• In resistant cases, corticosteroids may be considered.

Associated Conditions

• Celiac disease is linked with other autoimmune diseases, including type 1 diabetes and thyroid disorders.
• Dermatitis herpetiformis is a skin manifestation associated with CD.

Environmental and Genetic Influences

• Environmental factors like infections and stress may trigger CD in susceptible individuals.
• Non-HLA genes also contribute to CD susceptibility, though their roles are not fully defined.

Summary

• HLA-DQ2 is a critical factor in CD, influencing genetic predisposition and immune response.
• Diagnosis combines genetic testing, serology, and biopsy.
• Treatment focuses on a gluten-free diet and managing nutritional deficiencies.