Small intestinal intraepithelial TCRγδ+ T lymphocytes are present in the premature intestine but selectively reduced in surgical necrotizing enterocolitis.

Weitkamp JH, Rosen MJ, Zhao Z, Koyama T, Geem D, Denning TL, Rock MT, Moore DJ, Halpern MD, Matta P, Denning PW
PLoS One. 2014 9 (6): e99042

PMID: 24905458 · PMCID: PMC4048281 · DOI:10.1371/journal.pone.0099042

BACKGROUND - Gastrointestinal barrier immaturity predisposes preterm infants to necrotizing enterocolitis (NEC). Intraepithelial lymphocytes (IEL) bearing the unconventional T cell receptor (TCR) γδ (γδ IEL) maintain intestinal integrity and prevent bacterial translocation in part through production of interleukin (IL) 17.

OBJECTIVE - We sought to study the development of γδ IEL in the ileum of human infants and examine their role in NEC pathogenesis. We defined the ontogeny of γδ IEL proportions in murine and human intestine and subjected tcrδ-/- mice to experimental gut injury. In addition, we used polychromatic flow cytometry to calculate percentages of viable IEL (defined as CD3+ CD8+ CD103+ lymphocytes) and the fraction of γδ IEL in surgically resected tissue from infants with NEC and gestational age matched non-NEC surgical controls.

RESULTS - In human preterm infants, the proportion of IEL was reduced by 66% in 11 NEC ileum resections compared to 30 non-NEC controls (p<0.001). While γδ IEL dominated over conventional αβ IEL early in gestation in mice and in humans, γδ IEL were preferential decreased in the ileum of surgical NEC patients compared to non-NEC controls (50% reduction, p<0.05). Loss of IEL in human NEC was associated with downregulation of the Th17 transcription factor retinoic acid-related orphan nuclear hormone receptor C (RORC, p<0.001). TCRδ-deficient mice showed increased severity of experimental gut injury (p<0.05) with higher TNFα expression but downregulation of IL17A.

CONCLUSION - Complimentary mouse and human data suggest a role of γδ IEL in IL17 production and intestinal barrier production early in life. Specific loss of the γδ IEL fraction may contribute to NEC pathogenesis. Nutritional or pharmacological interventions to support γδ IEL maintenance in the developing small intestine could serve as novel strategies for NEC prevention.

MeSH Terms (16)

Animals Cells, Cultured Enterocolitis, Necrotizing Female Gene Expression Regulation Humans Infant, Newborn Infant, Premature Interleukin-17 Intestine, Small Male Mice Mice, Inbred C57BL Occludin Receptors, Antigen, T-Cell, gamma-delta T-Lymphocyte Subsets

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