Weaning is associated with an upregulation of expression of inflammatory cytokines in the intestine of piglets.

Cytokines play a central role in immune cell response, but they also participate in the maintenance of tissue integrity. Changes in the cytokine network of the pig gut may be expected at weaning, because abrupt changes in dietary and environmental factors lead to important morphological and functional adaptations in the gut. This study measured the gene expression of 6 inflammatory cytokines along the small intestine (SI) and the proximal colon in 28-d-old piglets (n = 45) at different time points (0, 1, 2, 5 and 8 d) postweaning, using RT-PCR. Villus-crypt architecture and enzymatic activities of lactase and sucrase in the SI were also examined. The results confirmed that weaning is associated with morphological and enzymatic changes in the SI. In addition, the data indicated that cytokine response in the gut could be divided into two periods: an early acute response (0 to 2 d postweaning) and a late long-lasting response (2 to 8 d postweaning). Between d 0 and d 2, the levels of IL-1beta, IL-6, and TNF-alpha messenger RNA (mRNA) increased. Marked upregulation of IL-1beta mRNA occurred in most parts of the intestine, whereas IL-6 and TNF-alpha mRNA markedly increased only at specific sites in the intestine. Between d 2 and d 8, the levels of IL-1beta, IL-6, and TNF-alpha mRNA rapidly returned to preweaning values, except that the level of TNF-alpha mRNA remained high in the distal SI. Levels of IL-12 subunit p40 (IL-12p40) and IL-18 mRNA also decreased, compared to those on d 0. Taken together, these results demonstrate that weaning in piglets is associated with an early and transient response in gene expression of inflammatory cytokines in the gut.