Abstract
Increasing studies show that gut microbiota play a central role in immunity, although the impact of the microbiota on mediation of thymic T cells throughout life is not well understood. Chickens have been shown to be a valuable model for studying basic immunology. Here, we show that changes in the gut microbiota are associated with the development of thymic T cells in young chickens. Our results showed that T-cell numbers in newborn chicks sharply increased from day 0 and peaked at day 49. Interestingly, the α-diversity score pattern of change in gut microbiota also increased after day 0 and continued to increase until day 49. We found that early antibiotic treatment resulted in a dramatic reduction in gut alpha diversity: principal component analysis (PCA) showed that antibiotic treatment resulted in a different cluster from the controls on days 9 and 49. In the antibiotic-treated chickens, we identified eight significantly different (p < 0.05) microbes at the phylum level and 14 significantly different (p < 0.05) microbes at the genus level, compared with the controls. Importantly, we found that antibiotic treatment led to a decreased percentage and number of T cells in the thymus when measured at days 9 and 49, as evaluated by flow cytometry. Collectively, our data suggest that intestinal microbiota may be involved in the regulation of T cells in birds, presenting the possibility that interventions that actively modify the gut microbiota in early life may accelerate the maturation of humoral immunity, with resulting anti-inflammatory effects against different pathogens.
Highlights
T cells, a type of lymphocyte, are central to the adaptive immune response [1]
Our results showed that the corticomedullary ratio of the thymus gland tended to decrease in the antibiotic-treated group compared with the controls on day 9 (p > 0.05)
These data suggest that antibioticinduced thymus dysbiosis may have significant long-term effects on chicken T cells
Summary
T cells, a type of lymphocyte, are central to the adaptive immune response [1]. T cells are derived from hematopoietic stem cells in the bone marrow, migrate to the thymus for differentiation and maturation, and are transported to the periphery to carry out immune functions [2]. The gut microbiota of preterm infants differs in composition from that of full-term infants. Preterm infants display a different developmental trajectory of their peripheral immune cell populations, compared with full-term infants [11]. Alteration of microbiota structure in early life as a consequence of antibiotic treatment in piglets can lead to excessive inflammation, local tissue damage, and a possible increased risk of immune-mediated disease following pathogenic bacterial infection [13]. Antibiotic-treated and germ-free mice show distinct intestinal T-cell receptor (TCR) repertoires compared with their wild-type controls, suggesting that microbial antigens alter Tcell development [14]. The chicken offered an excellent animal model in which to further study the relationship between the host immunity and gut microbiota
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