Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Zn serves as a powerful feed additive to reduce post-weaning diarrhoea in pigs. However, the mechanisms responsible for Zn-associated effects on the adaptive immune responses following feeding of a very high dosage of Zn remain elusive. In this study, we examined the T-cell response in gut-associated lymphatic tissues of seventy-two weaned piglets. Piglets received diets with 57 mg Zn/kg (low Zn concentration, LZn), 164 mg Zn/kg (medium Zn concentration, MZn) or 2425 mg Zn/kg (high Zn concentration, HZn) mg Zn/kg feed for 1, 2 or 4 weeks. We observed that feeding the HZn diet for 1 week increased the level of activated T-helper cells (CD4<jats:sup>+</jats:sup> and CD8<jats:italic>α</jats:italic><jats:sup>dim</jats:sup>) compared with feeding MZn and LZn (<jats:italic>P</jats:italic><0·05). In addition, we observed higher transcript amounts of interferon <jats:italic>γ</jats:italic> and T-box 21 (<jats:italic>TBET</jats:italic>) in the HZn group compared with the MZn and LZn groups (<jats:italic>P</jats:italic><0·05). A gene set enrichment analysis revealed an over-representation of genes associated with ‘cytokine signalling in immune system’. Remarkably, feeding of a very high Zn dosage led to a switch in the immune response after 2 weeks. We detected higher relative cell counts of CD4<jats:sup>+</jats:sup>CD25<jats:sup>high</jats:sup> regulatory T-helper cells (<jats:italic>P</jats:italic><0·05) and a higher expression of forkhead box P3 (<jats:italic>FOXP3</jats:italic>) transcripts (<jats:italic>P</jats:italic><0·05). After 4 weeks of feeding a high-dosage Zn diet, the relative CD4<jats:sup>+</jats:sup> T-cell count (<jats:italic>P</jats:italic><0·05) and the relative CD8<jats:italic>β</jats:italic><jats:sup>+</jats:sup> T-cell count (<jats:italic>P</jats:italic><0·1) were reduced compared with the MZn group. We hypothesise that after 1 week the cellular T-helper 1 response is switched on and after 2 weeks it is switched off, leading to decreased numbers of T-cells.</jats:p>