Flow cytometric analysis of duodenal intraepithelial lymphocytes (celiac lymphogram): A diagnostic test for celiac disease.

Celiac disease (CD) diagnosis in adults and certain cases of children mainly relies on the assessment of histopathological features in duodenal biopsies. However, none of the histological findings that characterize CD are pathognomonic. This, in addition to the clinical heterogeneity of the disease and the presence of seronegative forms, makes the diagnosis of CD still a challenge. A hallmark of the celiac mucosa is the elevated number of TCRγδ intraepithelial lymphocytes (IEL) in the epithelium, which may remain increased even long after gluten withdrawal. Active disease is also characterized by the decreased CD3- IEL subset. The use of flow cytometry enables a precise cell counting and phenotyping, allowing the ascertainment of both TCRγδ+ and CD3- IEL subsets, what is known as the "IEL lymphogram." Although determination of this lymphogram has become a routine evaluation tool in numerous hospitals, standardization of the technical method will guarantee an accurate performance in order to become a pivotal technique for CD diagnosis. Here we describe the protocol to process duodenal biopsies in order to obtain the IELs from the mucosa and to characterize lymphocyte populations by flow cytometry to obtain the IEL lymphogram.