Impaired intestinal mucosal immunity is associated with the imbalance of T lymphocyte sub-populations in intrauterine growth-restricted neonatal piglets

Intrauterine growth restriction (IUGR) impairs the immunity of both piglets and humans. We hypothesized that the poor cytokine secreting ability of the small intestines of IUGR neonatal piglets might be associated with lower CD4+ and CD8+ T lymphocytes. Therefore, we used neonatal piglets as IUGR models to investigate the effects of IUGR on the CD4+ and CD8+ T lymphocyte cell populations. Six normal-birth-weight (NBW) and six IUGR neonatal piglets were chosen and divided into NBW and IUGR groups, respectively. The cytokine and immunoglobulin levels in the blood; the CD4+ and CD8+ T lymphocyte contents in the thymus, blood, spleen, mesenteric lymph nodes, jejunum and ileum; and the distribution of CD4+ and CD8+ T lymphocytes in the ileum were measured. We further compared the gene expression and protein distribution of MHC-II in the jejunum and ileum of the NBW and IUGR neonatal piglets. The results showed that the IUGR piglets exhibited lower (P < 0.05) serum levels of IL1β, IL2 and IL10, as well as increased percentages of CD8 cells in the blood, spleen and thymus (P < 0.05) and increased CD4 gene expression in the thymus (P < 0.05). However, the CD4:CD8 ratio in the blood was decreased (P < 0.05), the CD8 content in the MLN was lowered (P < 0.05), and the expression of the CD4, CD8 and MHC-II genes was down-regulated (P < 0.05) in the jejunum and ileum of the IUGR piglets compared with those of the NBW piglets. The results suggest that impaired intestinal mucosal immunity is associated with an imbalance in the T lymphocyte sub-populations in IUGR neonatal piglets.