Interleukin-17 producing cells in swine induced by microbiota during the early postnatal period - a brief research report

Interleukin-17A (IL-17) is a pro-inflammatory cytokine involved in the immune response to many pathogens playing also a role in certain chronic and autoimmune diseases. The presented study focused on the early postnatal development of IL-17 producing cells in swine. In agreement with previous studies, alpha beta T-helper (CD3+CD4+) and gamma delta T (CD3+TCR gamma delta+) cells were found to be the major producers of IL-17. In newborn conventional piglets, alpha beta T-helper cells positive for IL-17 were almost undetectable, but their frequency increased markedly with age in all issues examined, i.e., blood, spleen, and mesenteric lymph nodes (MLN). Additional analyses of CD8 and CD27 expression showed that the main alpha beta T-helper producers of IL-17 has CD8+CD27- phenotype in all tissues. IL-17 positive CD8+CD27+ alpha beta T-helper subpopulation was found only in blood and spleen. The production of IL17 in CD8-CD27+ alpha beta T-helper cells was always minor. In contrast, gamma delta T cells positive for IL-17 did not show a similar age-dependent increase in blood and spleen, whereas they increased in MLN. Because of the age-dependent increase in conventional animals, we included a comparison with germ-free piglets to show that the increase in IL-17 positive cells was clearly depended on the presence of the microbiota as the production in germ-free animals was negligible without any age-dependent increase.

Automated summary

This study focused on the early development of IL-17 producing cells in swine, finding that alpha beta T-helper and gamma delta T cells are the major producers of IL-17. The frequency of IL-17 positive alpha beta T-helper cells increased with age, while IL-17 positive gamma delta T cells showed an increase only in MLN. CD8+CD27- alpha beta T-helper cells were the main producers in all tissues, while IL-17 positive CD8+CD27+ alpha beta T-helper cells were found only in blood and spleen. The presence of microbiota was found to be crucial for the increase in IL-17 positive cells, as germ-free animals showed negligible production without age-dependent increase.