Evaluation of the Lymphocyte Subpopulations in the Normal Mucosa of the Upper Digestive Tract

The macro and microscopic findings of the upper gastrointestinal tract are useful in the differential diagnosis of digestive diseases such as Crohn's or celiac diseases. However, the histopathological findings (duodenal lymphocytosis, atrophy, chronic inflammatory infiltrate, etc.) are generally not pathognomonic, and there is a great overlap between different inflammatory diseases. The study of lymphocyte subpopulations of the intestine has shown its usefulness in cases of celiac disease that are difficult to diagnose. In patients with celiac disease, lymphocytes that infiltrate the duodenum present a specific pattern with increased percentage of TCRgẟ+ lymphocytes and reduced percentage of CD3- lymphocytes. However, it is currently unknown if other inflammatory diseases (e.g. Crohn's disease) have specific lymphocyte subpopulations that could be of great diagnostic aid. One of the main problems in establishing patterns associated with disease is the absence of immunological studies carried out in healthy individuals. Most of the studies include, as a control group, patients who undergo gastroscopy for the study of upper digestive symptoms and have microscopically normal duodenal biopsy. This is a heterogeneous population that includes, among others, patients with functional pathology in whom the existence of low-grade inflammatory phenomena has been suggested. Therefore, patients with digestive symptoms are not good controls to establish normal patterns of intestinal immunity.