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Changes in the T cell response during gut maturation in young rats - effects of feeding phytohaemagglutinin (PHA), microbial protease and natural weaning

Wang, Jing (2013) MOBN13 20122
Degree Projects in Molecular Biology
Abstract
Popular science summary:

Mammals are born with relatively immature digestive and immune systems. The functional maturation of these systems takes place at weaning (dietary change from milk to solid food). The activation of immune system occurs due to new antigens from new diet and changed microflora. It has been shown in rat model that activation of adaptive immunity can influence functional development of gastrointestinal tract. Moreover, feeding with lectin phytohaemagglutinin (PHA) as a provocative agent, it has been shown that gut maturation as well as immune system activation takes place precociously in neonatal rats. Furthermore, it has been recently demonstrated that digestive proteases can also stimulate the functional... (More)
Popular science summary:

Mammals are born with relatively immature digestive and immune systems. The functional maturation of these systems takes place at weaning (dietary change from milk to solid food). The activation of immune system occurs due to new antigens from new diet and changed microflora. It has been shown in rat model that activation of adaptive immunity can influence functional development of gastrointestinal tract. Moreover, feeding with lectin phytohaemagglutinin (PHA) as a provocative agent, it has been shown that gut maturation as well as immune system activation takes place precociously in neonatal rats. Furthermore, it has been recently demonstrated that digestive proteases can also stimulate the functional development of gut, however the involvement of immune system activation in protease-provoked maturation was not estimated. Thus, the main objective was to elucidate any changes in the lymphoid organs and blood during induced maturation after dietary provocation with the exogenous protease or PHA in comparison to changes that naturally occur at weaning.

In the project, all studies were done using a rat model. To study natural changes, four groups of rats at different ages were used: the suckling rats (14-d old), the weaning (21-d old), one week after weaning (28-d old) and adult (35, 36-d old). To study changes after dietary provocation, the 14d-old, suckling rats were orally fed a single dose of PHA and protease in order to investigate the acute and later effects on the immune system, while water-fed pups were used as controls. All rat pups were anesthetized prior to organ collection and then thymus, spleen, mesenteric lymph nodes (MLNs) and blood were collected. Flow cytometry was performed to study changes in lymphocyte subpopulations such as T- (CD3+), B- (CD45RA+CD161-), T helper (CD4+CD8-) and T cytotoxic (CD4-CD8+) cells of mentioned organs and histology technique was used to study morphological changes in the thymus, spleen and MLNs.

Twenty four hours after treatment (acute phase), PHA or protease led to obvious changes in secondary lymphoid organs (spleen and MLNs), but not in primary lymphoid organ (thymus). For example, the organ weight and cell quantity were decreased in spleen, but were increased in MLNs. Moreover, the number of CD3+ T cells in spleen and MLNs were increased. While after repeated PHA treatment (late phase), there were obvious changes mainly in the thymus, including decreased thymus weight and increased T cell proportion (CD3+). Based on these results, conclusions are drawn as follows. At acute phase, T cells, especially T cytotoxic cells, in peripheral immune organs, were activated after oral treatment (PHA and protease) and then migrated to intestinal inflammatory sites. Moreover, T cells activation between precociously induced maturation and normal development was found to be similar.

Advisor: Olena Prykhod’ko
Master´s Degree Project 45 credits in Immunology 2013
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Wang, Jing
supervisor
organization
course
MOBN13 20122
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
4057011
date added to LUP
2013-09-19 14:35:56
date last changed
2013-09-19 14:35:56
@misc{4057011,
  abstract     = {Popular science summary:

Mammals are born with relatively immature digestive and immune systems. The functional maturation of these systems takes place at weaning (dietary change from milk to solid food). The activation of immune system occurs due to new antigens from new diet and changed microflora. It has been shown in rat model that activation of adaptive immunity can influence functional development of gastrointestinal tract. Moreover, feeding with lectin phytohaemagglutinin (PHA) as a provocative agent, it has been shown that gut maturation as well as immune system activation takes place precociously in neonatal rats. Furthermore, it has been recently demonstrated that digestive proteases can also stimulate the functional development of gut, however the involvement of immune system activation in protease-provoked maturation was not estimated. Thus, the main objective was to elucidate any changes in the lymphoid organs and blood during induced maturation after dietary provocation with the exogenous protease or PHA in comparison to changes that naturally occur at weaning. 

In the project, all studies were done using a rat model. To study natural changes, four groups of rats at different ages were used: the suckling rats (14-d old), the weaning (21-d old), one week after weaning (28-d old) and adult (35, 36-d old). To study changes after dietary provocation, the 14d-old, suckling rats were orally fed a single dose of PHA and protease in order to investigate the acute and later effects on the immune system, while water-fed pups were used as controls. All rat pups were anesthetized prior to organ collection and then thymus, spleen, mesenteric lymph nodes (MLNs) and blood were collected. Flow cytometry was performed to study changes in lymphocyte subpopulations such as T- (CD3+), B- (CD45RA+CD161-), T helper (CD4+CD8-) and T cytotoxic (CD4-CD8+) cells of mentioned organs and histology technique was used to study morphological changes in the thymus, spleen and MLNs.

Twenty four hours after treatment (acute phase), PHA or protease led to obvious changes in secondary lymphoid organs (spleen and MLNs), but not in primary lymphoid organ (thymus). For example, the organ weight and cell quantity were decreased in spleen, but were increased in MLNs. Moreover, the number of CD3+ T cells in spleen and MLNs were increased. While after repeated PHA treatment (late phase), there were obvious changes mainly in the thymus, including decreased thymus weight and increased T cell proportion (CD3+). Based on these results, conclusions are drawn as follows. At acute phase, T cells, especially T cytotoxic cells, in peripheral immune organs, were activated after oral treatment (PHA and protease) and then migrated to intestinal inflammatory sites. Moreover, T cells activation between precociously induced maturation and normal development was found to be similar.

Advisor: Olena Prykhod’ko
Master´s Degree Project 45 credits in Immunology 2013
Department of Biology, Lund University},
  author       = {Wang, Jing},
  language     = {eng},
  note         = {Student Paper},
  title        = {Changes in the T cell response during gut maturation in young rats - effects of feeding phytohaemagglutinin (PHA), microbial protease and natural weaning},
  year         = {2013},
}