The gut is one of the body’s major immune structures, and the gut mucosa, which contains intestinal epithelium and subepithelial immune cells, is the primary site for eliciting local immune responses to foreign antigens. Intestinal immune system development in pigs is a transitional period during birth and weaning. This study compares the morphological and immunological differences in the small intestine of neonatal and weaned piglets to potentially prevent intestinal infectious diseases in neonatal piglets. Histological analyses of weaned piglet intestines showed increased crypt depth, higher IEL count, and larger ileal Peyer’s patches compared with those of neonates. Additionally, the ileal villi of weaned piglets were longer than those of neonatal piglets, and claudin-3 protein expression was significantly higher in weaned than in neonatal piglets. The numbers of CD3⁺ T, goblet, and secretory cells were also higher in the small intestines of weaned piglets than in those of neonates. No significant differences were observed in the secretory IgA-positive cell number in the jejunum of weaned and neonatal piglets. The mRNA expression of most pattern recognition receptors genes in the duodenum and jejunum was higher in the weaned than neonatal piglets; however, the opposite was true in the ileum. The mRNA levels of IL-1β and TNF-α in the jejunal and ileal mucosa were higher in weaned piglets than in neonatal piglets. There were significantly fewer CD3⁺, CD4⁺, and CD8⁺ T cells from peripheral blood-mononuclear cells in neonatal piglets. Our study provides insights regarding the different immune mechanisms within the small intestines of 0- and 21-day-old piglets. Studies on the additional developmental stages and how differences in the small intestines affect the response of pigs to pathogens remain warranted.

中文翻译：

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强调新生仔猪和断奶仔猪小肠之间差异的单盲研究

肠道是人体的主要免疫结构之一，肠道粘膜（包含肠上皮和上皮下免疫细胞）是引起对外源抗原的局部免疫反应的主要部位。猪的肠道免疫系统发育是出生和断奶期间的过渡期。这项研究比较了新生仔猪和断奶仔猪小肠的形态和免疫学差异，以潜在地预防新生仔猪的肠道传染病。对断奶仔猪肠道的组织学分析显示，与新生儿相比，断奶小猪的隐窝深度增加，IEL计数更高，回肠派伊尔斑块更大。此外，断奶仔猪的回肠绒毛比新生仔猪长，断奶仔猪中claudin-3蛋白的表达明显高于新生仔猪。CD3的数量断奶仔猪的小肠中的⁺ T，杯状细胞和分泌细胞也比新生仔猪的小肠中更高。断奶仔猪和新生仔猪空肠中分泌型IgA阳性细胞数量未见显着差异。断奶仔猪中十二指肠和空肠中大多数模式识别受体基因的mRNA表达均高于新生仔猪。然而，在回肠中则相反。断奶仔猪空肠和回肠粘膜中IL-1β和TNF-α的mRNA水平高于新生仔猪。CD3 ⁺，CD4 ⁺和CD8 ^+的数量明显减少新生仔猪外周血单核细胞中的T细胞。我们的研究提供了关于0日龄和21日龄仔猪小肠内不同免疫机制的见解。仍需要对其他发育阶段以及小肠差异如何影响猪对病原体的反应进行研究。