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.