Development of lntraepithelial Cellsin the Porcine Small Intestine

Abstract

The number, phenotype, localisation and development of intraepithelial lymphocytes (IEL) from duodenum (Du) and ileum (I1) were studied by immunohistochemistry (IHC) and light and electron microscopy in unweaned (0-7 weeks old) and six months-old pigs. Developmental changes at birth showed that 38% of the total lymphocytes in the villi were IEL, mainly of the CD2+CD4-CD8-double negative (DN) phenotype. That proportion rose to over 50% at week 5 after birth, resembling adult proportion, although still with fewer cells than in adult pigs. CD4+ cells appeared relatively early in life although they were confined to the lamina propria (LP) and CD8+ cells were found only in low numbers. In the villi of adult animals, almost'half of the total number of lymphocytes were IEL (49% Du, 52% I1). Over half of these IEL (52% Du, 53% I1) showed the CD2+CD4-CD8+ phenotype and were localized at the epithelium's basement membrane. Numerous (43% Du, 42% I1) DN IEL were found grouped at the enterocyte nucleus level and relatively few (5% in Du and I1) granular IEL were found apically in the epithelium. These proportions were homogeneously maintained along the villi's tip, middle and bottom, suggesting that the IEL may have their origin in the LP. Therefore, the IEL compartment in the porcine intestine develops slowly with age and is actually composed by a heterogeneous population of cells (null, DN and CD8+). These results may explain the increased susceptibility of young animals to disease during the lactation period and should be taken into account when functional studies are carried out with IEL. The quantitative results of this paper established a model for studies on the effect of age, diet, normal flora, infection and oral immunization on the IEL of the gut.

The combined use of triacylglycerols containing medium-chain fatty acids and exogenous lipolytic enzymes as an alternative to in-feed antibiotics in piglets: concept, possibilities and limitations. An overview

“…IEL are Tlymphocytes, mainly of the CD8 + phenotype, of which the functions have not been entirely elucidated. It is accepted that they play a central role as a first line of defence against foreign luminal antigens (pathogens, proteins), in the induction of apoptosis of epithelial cells and in the conservation of the mucosal integrity (Vega-Lopez et al 2001). This is in line with the observations of Czernichow et al (1996) showing that enterally infused MCTAG enhanced mucosal mass and favoured epithelial cell renewal in the proximal intestine in rats.…”

BOARD-INVITED REVIEW: Porcine mucosal immunity of the gastrointestinal tract1

“…Vega-Lopez et al (2001) observed similar developmental changes in IEL and proposed that the delayed maturation of IEL might be positively correlated with the increased disease susceptibility of young pigs. Even though there is more to learn about IEL, particularly in domestic animal species, their location among the intestinal epithelia is indicative of their importance as immune regulators and effectors at the luminal-epithelial interface.…”

Stimulation of gp91 Phagocytic Oxidase and Reactive Oxygen Species in Neutrophils by an AvirulentSalmonella entericaSerovar Infantis Strain Protects Gnotobiotic Piglets from Lethal Challenge with Serovar Typhimurium Strain F98 without Inducing Intestinal Pathology

“…However, these studies differ from ours in a number of respects since piglets were challenged with virulent strain LT2 8 days after the protective inoculation, whereas the effect that we report here occurred within 48 h after challenge. Although numerous studies have shown that enterocyte pathology is associated with Th1 cytokines, such as gamma interferon and tumor necrosis factor alpha (TNF-␣) (1,17,21,36), insignificant numbers of lymphocytes are found in the intestines of gnotobiotic piglets (29,42). This may indicate that within the first week after birth (the duration of our study) the production of inflammatory cytokines is not sufficient to induce the severe pathology that we observed in F98-infected piglets.…”