Origin and immunophenotype of aberrant IEL in RCDII patients

► Aberrant intra-epithelial lymphocytes (IELs) are the hallmark of refractory coeliac disease type II RCDII. ► Our data indicates that aberrant IELs in duodenal biopsies of RCDII patients originate from deranged developing precursor T-lymphocytes, while the various populations display heterogeneous TCR gene rearrangements, but all contain high levels of granzyme B. ► Only patients harboring the most mature aberrant IEL population developed an EATL. ► TCR-beta gene rearrangement analysis in addition to phenotypical identification of aberrant IELs could be useful to identify at risk aberrant IEL population.