Immunohistochemical assessment of duodenal mucosal gamma/delta receptor-expressing T-lymphocytes as a diagnostic adjunct for pediatric celiac disease.

Celiac disease (CeD) diagnosis can be challenging in cases with borderline or discrepant serological and histopathological findings. While intraepithelial lymphocytes (IELs) are characteristic of CeD, conventional counting methods lack specificity and overlap with other enteropathies. Gamma/delta (γ/δ) T-lymphocytes quantification was identified to be more specific but require validation in formalin-fixed paraffin-embedded (FFPE) biopsies. This study aimed to assess the IEL using immunohistochemistry (IHC) for anti-CD3 and anti-TCRγ/δ (H-41) antibodies on FFPE duodenal mucosal endoscopic biopsies in pediatric CeD patients versus non-CeD controls. 64 pediatric duodenal biopsies (34 untreated CeD, 30 non-CeD) were retrospectively analyzed for histopathologic features of CeD with special attention to IEL count using H&E (hematoxylin and eosin), anti-CD3, anti-TCRγ/δ IHC. The TCRγ/δ+:CD3+ ratio were assessed. It was found that CeD patients had significantly higher IEL counts by H&E (63.5 ± 13.5 vs. 43.2 ± 10.6), CD3 (83.9 ± 21.0 vs. 48.7 ± 11.8), TCRγ/δ (27.7 ± 11.6 vs. 3.5 ± 5.7) and TCRγ/δ+:CD3+ ratio (33.8 ± 13.2 % vs. 6 ± 8.6 %) compared to non-CeD (P = 0.001). IEL densities increased in higher Marsh-Oberhuber grades, with a significant trend for CD3+ IELs. Diagnostic performance was highest for anti-TCRγ/δ followed by TCRγ/δ+:CD3+ ratio, then anti-CD3 outperforming H&E. Overall, the quantification of TCRγ/δ + IELs and TCRγ/δ+:CD3+ ratio by IHC offers superior diagnostic accuracy for pediatric CeD compared to H&E and CD3. Incorporating TCRγ/δ IHC enhances differentiation of CeD from mimicking enteropathies, particularly with borderline and equivocal histology or serology. Further validation and standardization with larger cohorts is recommended.