Intra-tissue Immune Response in Pediatric Patients with Short Bowel Syndrome

Introduction: Short bowel syndrome (SBS) is a rare disease characterized by inadequate nutrient absorption caused by severe reduction of the intesti- nal mucosal surface. The study immunologically characterized the bowel layers’ lymphocyte T infil- trate and evidenced its alterations through a qualitative analysis. Methods: Pediatric SBS patients who underwent bowel surgery between July 2018 and March 2019 were enrolled. Full thickness small bowel samples were taken and processed. The tissue was dissected and the tissue-infiltrat- ing T lymphocytes (TILs) were isolated, cloned and expanded. The pheno- typic characterization was performed using flow cytometry and anti-CD4 and CD8. The clones were stimulated and phenotypically characterized through ELISA test, evaluating the production of IFN-γ, IL-4, IL-17, IL-10. Student’s t-test was used for statistical analysis and statistical significance was considered as p<0,05. Results: Twelve patients were enrolled, with a median age of 3 years and 9 months (range: 2 months - 18 years and 5 months) and a median length of the small intestine of 40 cm (range: 19 cm - 67 cm). All patients were parenteral nutrition dependent, 92% received also enteral nutrition and 58% received intestinal decontamination. The intestinal samples of ten of these patients were analyzed and TILs were isolated in 60% of cases. 49 T cell clones were obtained and the phenotypic characteriza- tion was made: 30 T helper lymphocytes (61.2%), 17 T cytotoxic (34.7%), 1 T double-positive CD4+CD8+ (2%), 1 T CD4-CD8- defined ɣδ (2%). We proceeded with the functional characterization: T helper lymphocytes are divided intoTh1 clones (20, 80.0%), T reg (1, 3.3%), Tnull (5, 16.7%), no Th2 clone, no Th0, no Th17. Cytotoxic T lymphocytes are classified into: Tc1 clones (12, 70.6%); Tcnull (5, 29.4%); no Tcreg clone, no Tc2, no Tc0, no Tc17. The correlation between the number of isolated T cell clones and the lack of intestinal decontamination therapy was not statistically signifi- cant (p-value=0,27). Conclusion: We hypothesize that the alteration of the immune balance of SBS patients, especially the acquisition of pro-inflammatory characteristics, is caused by the dependence on parenteral nutrition and the deprivation of enteral nutrition or by the intestinal dysbiosis.