🌾 tTG-IgA Antibody Testing Simulator

Gluten Exposure and Mucosal Immune Activation

Gluten peptides breach the epithelium and activate an adaptive immune reaction.

• Gliadin: Trigger antigen (Placeholder short note)
• Villi: Barrier crossed (Placeholder short note)
• APCs/T-cells: Immune cells (Placeholder short note)
• Chronic: Onset (Placeholder short note)

Gluten crosses the mucosal barrier

Placeholder: gluten peptides enter the lamina propria.

HLA-DQ2/DQ8 presentation

Placeholder: deamidated peptides are presented to T-cells.

tTG-IgA Antibody Generation Against Tissue Transglutaminase

Plasma cells secrete IgA antibodies targeting the tTG autoantigen.

• IgA: Antibody class (Placeholder short note)
• tTG (TG2): Autoantigen (Placeholder short note)
• 0-100 U/mL: Titer range (Placeholder short note)
• ~20 U/mL: Cutoff (typical) (Placeholder short note)

Deamidation drives autoantibody formation

Placeholder: tTG deamidates gliadin, forming neo-epitopes.

IgA binds tTG on villus surface

Placeholder: antibodies deposit at the epithelial subsurface.

Measuring Total Serum IgA to Validate the tTG-IgA Assay

Total IgA must be checked alongside tTG-IgA to confirm test reliability.

• >0.7 g/L: Normal total IgA (Placeholder short note)
• <0.07 g/L: Deficiency threshold (Placeholder short note)
• ~1 in 500: Population prevalence (Placeholder short note)
• Nephelometry: Test type (Placeholder short note)

Why total IgA matters

Placeholder: an IgA-based test needs adequate IgA to work.

Gauge reading and reference range

Placeholder: gauge shows deficient to normal total IgA.

Selective IgA Deficiency and the False-Negative Trap

IgA-deficient patients can test falsely negative despite having celiac disease.

• ~2-3%: Celiac + IgA deficiency (Placeholder short note)
• High: Risk when deficient (Placeholder short note)
• IgG-based: Backup test (Placeholder short note)
• IgA <0.07 g/L: Flag trigger (Placeholder short note)

Warning flag logic

Placeholder: low total IgA raises a false-negative warning.

Clinical consequence

Placeholder: celiac disease may be missed without a backup test.

Combining Titer and Total IgA into a Final Result

Final interpretation weighs both the tTG-IgA titer and total IgA validity.

• Refer biopsy: Positive + valid (Placeholder short note)
• Celiac unlikely: Negative + valid (Placeholder short note)
• Order IgG test: Any + deficient (Placeholder short note)
• 10-20 U/mL: Equivocal band (Placeholder short note)

Decision pathway summary

Placeholder: combine titer, IgA level, and flags for a verdict.

Next clinical steps

Placeholder: biopsy, retest, or IgG-based confirmation as needed.