Celiac Index

The commanders of the immune attack — they see gluten displayed by HLA molecules and order the rest of the immune system to fight.

CD4+ T cells (also called helper T cells) are a type of white blood cell that coordinates the adaptive immune response. "CD4" refers to a surface protein they carry. Their job is to inspect peptide fragments displayed on HLA-DQ molecules on the surface of antigen-presenting cells, and — if they recognise a threat — activate a full immune response.

In celiac disease, CD4+ T cells are the central drivers of chronic intestinal damage. Once activated by deamidated gliadin peptides, they remain sensitized — responding to every future gluten exposure.

How They Get Activated in Celiac

gliadin peptides cross the intestinal barrier and are modified by tissue-transglutaminase (deamidated)
Antigen-presenting cells (APCs) pick up the modified peptides and display them in their HLA-DQ2 or DQ8 groove
CD4+ T cells with the matching T cell receptor (TCR) recognise the HLA–peptide complex
The T cells activate, proliferate, and release cytokines (IFN-γ, IL-21, etc.)
Cytokines drive inflammation, villous-atrophy, and further immune cell recruitment

Why the Response Is Permanent

Unlike a one-time infection, where immune memory eventually wanes, celiac disease represents a chronic low-grade antigen exposure as long as gluten is consumed. The immune system doesn't forget — it has memory T cells that respond faster and stronger on each subsequent gluten encounter.

This is why celiac is a lifelong condition: the sensitized T cell population persists indefinitely. A gluten-free-diet removes the trigger but doesn't erase immune memory.

Gluten-Specific T Cells as Diagnostic Tools

Researchers have developed HLA-DQ–gluten tetramers — engineered molecules that bind directly to gluten-specific T cell receptors. These can be used in blood tests to detect gluten-reactive T cells even in patients not currently consuming gluten, potentially enabling diagnosis without a gluten-challenge. See research directions.

Role in Tolerance Induction Research

tolerance-induction therapies (e.g. Nexvax2, KAN-101) aim to re-train CD4+ T cells to ignore gluten peptides — turning an immune reaction into tolerance. This is the most ambitious research direction as it would be genuinely disease-modifying.

Referenced In

mechanism | causes | research_plan | glossary