A New Intraepithelial γδ T-Lymphocyte Marker for Celiac Disease Classification in Formalin-Fixed Paraffin-Embedded (FFPE) Duodenal Biopsies

Background The histopathologic diagnosis of celiac disease (CD) may be challenging when the duodenal biopsies mucosal injury is limited. Intraepithelial T-lymphocytes (IELs) can be useful to characterize the degree of mucosal inflammation. A small fraction of IELs expresses the gamma delta T-cell receptor (named gamma delta-IELs), whose density, determined by flow cytometry or frozen section immunohistochemistry (IHC), is a specific marker for CD. Aim To establish a new IHC assay for gamma delta-IELs applicable to formalin-fixed paraffin-embedded (FFPE) duodenal biopsies. Methods We analyzed gamma delta-IELs using IHC in 138 duodenal biopsies using a standard IHC staining protocol with a new monoclonal antibody H-41. IELs were quantitated with digital image analysis. Results Compared to those in non-celiac controls (n = 51), gamma delta-IEL density was significantly increased in newly diagnosed celiac disease patients (n = 22, p < 0.0001). In ROC-curve analysis, the cutoff of 6.5 gamma delta-IELs/100 enterocytes distinguished optimally active CD patients from non-celiac controls (sensitivity 96%, specificity 95%). gamma delta-IEL density in CD patients on a gluten-free diet (n = 53) were also higher than in controls (p < 0.0001), but lower than those in newly diagnosed CD (p < 0.0001). The diagnostic value of gamma delta-IELs outperformed that of CD3 + IELs in both patient groups. gamma delta-IELs were better than CD3 + IELs distinguishing between celiac disease and conditions histologically mimicking celiac disease (n = 12). Conclusions Intraepithelial gamma delta T-lymphocytes can be stained and quantitated reliably in FFPE duodenal biopsies. The results showed excellent specificity and sensitivity for celiac disease. The new IHC method of detection of gamma delta-IELs is a promising addition to the routine histopathologic assessment methodology of celiac disease.

Automated summary

A new IHC method has been developed to reliably detect and quantify gamma delta-IELs in FFPE duodenal biopsies, showing excellent specificity and sensitivity for celiac disease. This new method is a promising addition to the routine histopathologic assessment of celiac disease.