TIA1 and mast cell tryptase in food allergy of children: Increase of intraepithelial lymphocytes expressing TIA1 associates with allergy

Background: Variability of symptoms and signs make the diagnosis of childre n's food allergy (FA) difficult. In addition, mechanisms and antigens invol ved vary with age. In young infants, cow's milk protein allergy is associat ed with an increase of cytotoxic intraepithelial lymphocytes (IELs) express ing T-cell-restricted intracellular antigen (TIA1). In the current study: t he significance of TIA1 in FA in older children of mainly preschool and sch ool age was analyzed and the findings correlated the with a detailed clinic al, endoscopic, and histopathologic analysis. Methods: The subjects of this study were 66 children (mean age, 7.9 years; range, 1-15), including 27 with untreated and 15 with treated FA, and 24 co ntrol subjects. The morphology of duodenal and antral biopsy specimens was evaluated, and the proportion of TIA1-positive IELs was counted from immuno stained sections. Quantification of mast cells with immunostaining for mast cell tryptase (MCT) was completed, with the estimation of diffuse extracel lular staining considered to indicate degranulation. Results: Patients with untreated FA showed an increase in the total number of TIA I-positive cells and IELs and of the TIA1/ IEL ratio. The number of mast cells in duodenal mucosa was decreased in children with FA, but no ass ociation with degranulation was observed. Endoscopic abnormalities were com mon in FA, but conventional histopathology showed no informative difference s. Conclusions: The significant increase of TIA1-positive IELs in duodenal tis sue specimens is associated with FA. The cytotoxicity of T lymphocytes seem s to play a role in the pathogenesis of gastrointestinal FA. Activation and mechanisms of action should be studied further.