Flow cytometric characterization of aberrant intraepithelial lymphocytes (IEL) in patients with complicated celiac disease

Celiac disease (CD) is an immunologically mediated intolerance triggered by gluten ingestion, leading to intestinal damage and systemic symptoms. Recurrent symptoms and slow mucosal healing, despite a strict gluten-free diet for >12 months, are suggestive of refractory celiac disease (RCD). It can further be classified into RCD I, associated with a normal profile of intraepithelial lymphocytes (IELs) and better prognosis, and RCD II, which involves clonal expansion of aberrant IELs and a higher risk of enteropathy-associated T-cell lymphoma (EATL) development. The distinction between the two types relies on flow cytometry (FC) to determine IEL immunophenotypes and detect aberrant populations indicative of RCD II. The aim of the study was to assess flow cytometry immunophenotyping and its significance in identifying aberrant IELs in patients with complicated celiac disease, providing a contrast with histological analysis. The study included 9 patients who had undergone the upper endoscopy procedure and whose biopsy samples were used to isolate IELs. The immunophenotypes were determined using FC, precisely the presence of markers CD45, CD103 and CD7, while sCD3, cCD3 and CD8 were crucial for the identification of aberrant IELs. Histological findings were compared with FC results, revealing discordance between the degree of mucosal damage and the amount of aberrant IELs. The results showed that FC is a method that provides distinction between sCD3 and cCD3 and accurate characterization of sCD3–/cCD3+ aberrant IELs. The real value of FC is demonstrated in a patient with 10-15 CD3+ infiltrated IELs/100 enterocytes, who was diagnosed with RCD II that progressed to EATL. Immunophenotypic characterization of IELs aims to improve the diagnosis and treatment of RCD, as well as recognition of patients with an increased risk of lymphoma development.