Immune System Development - Revision history

Z8600021 at 00:45, 25 February 2020

2020-02-25T00:45:43Z

← Older revision		Revision as of 11:45, 25 February 2020
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			'''Essential cell-extrinsic requirement for PDIA6 in lymphoid and myeloid development'''{{#pmid:31985756\|PMID31985756}} "In a forward genetic screen of N-ethyl-N-nitrosourea (ENU)-induced mutant mice for aberrant immune function, we identified mice with a syndromic disorder marked by growth retardation, diabetes, premature death, and severe lymphoid and myeloid hypoplasia together with diminished T cell-independent (TI) antibody responses. The causative mutation was in Pdia6, an essential gene encoding protein disulfide isomerase A6 (PDIA6), an oxidoreductase that functions in nascent protein folding in the endoplasmic reticulum. The immune deficiency caused by the Pdia6 mutation was, with the exception of a residual T cell developmental defect, completely rescued in irradiated wild-type recipients of PDIA6-deficient bone marrow cells, both in the absence or presence of competition. The viable hypomorphic allele uncovered in these studies reveals an essential role for PDIA6 in hematopoiesis, but one extrinsic to cells of the hematopoietic lineage. We show evidence that this role is in the proper folding of Wnt3a, BAFF, IL-7, and perhaps other factors produced by the extra-hematopoietic compartment that contribute to the development and lineage commitment of hematopoietic cells."

	* '''Paraxial Mesoderm Is the Major Source of Lymphatic Endothelium'''{{#pmid:31130354\|PMID31130354}} " Endothelial cells (ECs), which line blood and lymphatic vessels, are generally described to come from the lateral plate mesoderm despite experimental evidence for a broader source of origin, including the paraxial mesoderm (PXM). Current dogma suggests that following specification from mesoderm, local environmental cues establish the distinct molecular and functional characteristics of ECs in different vascular beds. Here we present evidence to challenge this view, showing that lymphatic EC fate is imprinted during transition through the PXM lineage. We show that PXM-derived cells form the lymphatic endothelium of multiple organs and tissues, with a more restricted contribution to blood vessel endothelium. By deleting Prox1 specifically in PXM-derived cells, we show that this lineage is indispensable for lymphatic vessel development. Collectively, our data establish lineage history as a critical determinant of EC specialization, a finding with broad implications for our understanding of vascular development and heterogeneity."		* '''Paraxial Mesoderm Is the Major Source of Lymphatic Endothelium'''{{#pmid:31130354\|PMID31130354}} " Endothelial cells (ECs), which line blood and lymphatic vessels, are generally described to come from the lateral plate mesoderm despite experimental evidence for a broader source of origin, including the paraxial mesoderm (PXM). Current dogma suggests that following specification from mesoderm, local environmental cues establish the distinct molecular and functional characteristics of ECs in different vascular beds. Here we present evidence to challenge this view, showing that lymphatic EC fate is imprinted during transition through the PXM lineage. We show that PXM-derived cells form the lymphatic endothelium of multiple organs and tissues, with a more restricted contribution to blood vessel endothelium. By deleting Prox1 specifically in PXM-derived cells, we show that this lineage is indispensable for lymphatic vessel development. Collectively, our data establish lineage history as a critical determinant of EC specialization, a finding with broad implications for our understanding of vascular development and heterogeneity."

	* '''Review - Key molecules in lymphatic development, function, and identification'''{{#pmid:29842991\|PMID29842991}} "While both blood and lymphatic vessels transport fluids and thus share many similarities, they also show functional and structural differences, which can be used to differentiate them. Specific visualization of lymphatic vessels has historically been and still is a pivot point in lymphatic research. Many of the proteins that are investigated by molecular biologists in lymphatic research have been defined as marker molecules, i.e. to visualize and distinguish lymphatic endothelial cells (LECs) from other cell types, most notably from blood vascular endothelial cells (BECs) and cells of the hematopoietic lineage. Among the factors that drive the developmental differentiation of lymphatic structures from venous endothelium, Prospero homeobox protein 1 (PROX1) is the master transcriptional regulator. PROX1 maintains lymphatic identity also in the adult organism and thus is a universal LEC marker. Vascular endothelial growth factor receptor-3 (VEGFR-3) is the major tyrosine kinase receptor that drives LEC proliferation and migration. The major activator for VEGFR-3 is vascular endothelial growth factor-C (VEGF-C). However, before VEGF-C can signal, it needs to be proteolytically activated by an extracellular protein complex comprised of Collagen and calcium binding EGF domains 1 (CCBE1) protein and the protease A disintegrin and metallopeptidase with thrombospondin type 1 motif 3 (ADAMTS3)."		* '''Review - Key molecules in lymphatic development, function, and identification'''{{#pmid:29842991\|PMID29842991}} "While both blood and lymphatic vessels transport fluids and thus share many similarities, they also show functional and structural differences, which can be used to differentiate them. Specific visualization of lymphatic vessels has historically been and still is a pivot point in lymphatic research. Many of the proteins that are investigated by molecular biologists in lymphatic research have been defined as marker molecules, i.e. to visualize and distinguish lymphatic endothelial cells (LECs) from other cell types, most notably from blood vascular endothelial cells (BECs) and cells of the hematopoietic lineage. Among the factors that drive the developmental differentiation of lymphatic structures from venous endothelium, Prospero homeobox protein 1 (PROX1) is the master transcriptional regulator. PROX1 maintains lymphatic identity also in the adult organism and thus is a universal LEC marker. Vascular endothelial growth factor receptor-3 (VEGFR-3) is the major tyrosine kinase receptor that drives LEC proliferation and migration. The major activator for VEGFR-3 is vascular endothelial growth factor-C (VEGF-C). However, before VEGF-C can signal, it needs to be proteolytically activated by an extracellular protein complex comprised of Collagen and calcium binding EGF domains 1 (CCBE1) protein and the protease A disintegrin and metallopeptidase with thrombospondin type 1 motif 3 (ADAMTS3)."

	* '''Tie1 is required for lymphatic valve and collecting vessel development'''{{#pmid:25576926\|PMID25576926}} "Tie1 is a receptor tyrosine kinase with broad expression in embryonic endothelium. Reduction of Tie1 levels in mouse embryos with a hypomorphic Tie1 allele resulted in abnormal lymphatic patterning and architecture, decreased lymphatic draining efficiency, and ultimately, embryonic demise. ... Our findings reveal a fundamental role for Tie signaling during lymphatic vessel remodeling and valve morphogenesis and implicate it as a candidate gene involved in primary lymphedema."

	* '''The Nobel Prize in Physiology or Medicine''' [http://www.nobelprize.org/nobel_prizes/medicine/laureates/2011/ 2011] Bruce A. Beutler and Jules A. Hoffmann ''for their discoveries concerning the activation of innate immunity'' and the other half to Ralph M. Steinman ''for his discovery of the dendritic cell and its role in adaptive immunity''.		* '''The Nobel Prize in Physiology or Medicine''' [http://www.nobelprize.org/nobel_prizes/medicine/laureates/2011/ 2011] Bruce A. Beutler and Jules A. Hoffmann ''for their discoveries concerning the activation of innate immunity'' and the other half to Ralph M. Steinman ''for his discovery of the dendritic cell and its role in adaptive immunity''.
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	\| {{Older papers}}		\| {{Older papers}}
			* '''Tie1 is required for lymphatic valve and collecting vessel development'''{{#pmid:25576926\|PMID25576926}} "Tie1 is a receptor tyrosine kinase with broad expression in embryonic endothelium. Reduction of Tie1 levels in mouse embryos with a hypomorphic Tie1 allele resulted in abnormal lymphatic patterning and architecture, decreased lymphatic draining efficiency, and ultimately, embryonic demise. ... Our findings reveal a fundamental role for Tie signaling during lymphatic vessel remodeling and valve morphogenesis and implicate it as a candidate gene involved in primary lymphedema."

	* '''Regulation of lymphatic-blood vessel separation by endothelial Rac1.'''{{#pmid:19906871\|PMID19906871}} "Sprouting angiogenesis and lymphatic-blood vessel segregation both involve the migration of endothelial cells, but the precise migratory molecules that govern the decision of blood vascular endothelial cells to segregate into lymphatic vasculature are unknown."		* '''Regulation of lymphatic-blood vessel separation by endothelial Rac1.'''{{#pmid:19906871\|PMID19906871}} "Sprouting angiogenesis and lymphatic-blood vessel segregation both involve the migration of endothelial cells, but the precise migratory molecules that govern the decision of blood vascular endothelial cells to segregate into lymphatic vasculature are unknown."

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	===Reviews===		===Reviews===
			{{#pmid:26980792}}

	{{#pmid:24861898}}		{{#pmid:24861898}}

Z8600021 at 13:16, 3 Haziran 2019

2019-06-03T13:16:21Z

← Older revision		Revision as of 00:16, 4 Haziran 2019
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	The maternal immune system also has specialised functions and cells associated with [[implantation]], ~~[[Placenta Development\|~~placenta ~~development]]~~ and pregnancy.		The maternal immune system also has specialised functions and cells associated with {{implantation}}, {{placenta}} and pregnancy.


	* '''During prenatal development''', maternal IgG antibodies are transferred from about {{GA}} week 13 from maternal blood across the placenta. Placenta syncytiotrophoblast cell endosomes bind IgG, in maternal blood lacunae, through neonatal Fc receptors.		* '''During prenatal development''', maternal IgG antibodies are transferred from about {{GA}} week 13 from maternal blood across the placenta. Placenta syncytiotrophoblast cell endosomes bind IgG, in maternal blood lacunae, through neonatal Fc receptors.
	* '''During early postnatal development''', maternal IgA, IgM, IgG antibodies are transferred from [[Normal_Development_-_Milk\|breast milk]] into the infant gastrointestinal tract.		* '''During early postnatal development''', maternal IgA, IgM, IgG antibodies are transferred from [[Normal_Development_-_Milk\|breast milk]] into the infant gastrointestinal tract.
	* '''During postnatal development''', the immune system matures..		* '''During postnatal development''', the immune system matures.


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			* '''Paraxial Mesoderm Is the Major Source of Lymphatic Endothelium'''{{#pmid:31130354\|PMID31130354}} " Endothelial cells (ECs), which line blood and lymphatic vessels, are generally described to come from the lateral plate mesoderm despite experimental evidence for a broader source of origin, including the paraxial mesoderm (PXM). Current dogma suggests that following specification from mesoderm, local environmental cues establish the distinct molecular and functional characteristics of ECs in different vascular beds. Here we present evidence to challenge this view, showing that lymphatic EC fate is imprinted during transition through the PXM lineage. We show that PXM-derived cells form the lymphatic endothelium of multiple organs and tissues, with a more restricted contribution to blood vessel endothelium. By deleting Prox1 specifically in PXM-derived cells, we show that this lineage is indispensable for lymphatic vessel development. Collectively, our data establish lineage history as a critical determinant of EC specialization, a finding with broad implications for our understanding of vascular development and heterogeneity."

			* '''Review - Key molecules in lymphatic development, function, and identification'''{{#pmid:29842991\|PMID29842991}} "While both blood and lymphatic vessels transport fluids and thus share many similarities, they also show functional and structural differences, which can be used to differentiate them. Specific visualization of lymphatic vessels has historically been and still is a pivot point in lymphatic research. Many of the proteins that are investigated by molecular biologists in lymphatic research have been defined as marker molecules, i.e. to visualize and distinguish lymphatic endothelial cells (LECs) from other cell types, most notably from blood vascular endothelial cells (BECs) and cells of the hematopoietic lineage. Among the factors that drive the developmental differentiation of lymphatic structures from venous endothelium, Prospero homeobox protein 1 (PROX1) is the master transcriptional regulator. PROX1 maintains lymphatic identity also in the adult organism and thus is a universal LEC marker. Vascular endothelial growth factor receptor-3 (VEGFR-3) is the major tyrosine kinase receptor that drives LEC proliferation and migration. The major activator for VEGFR-3 is vascular endothelial growth factor-C (VEGF-C). However, before VEGF-C can signal, it needs to be proteolytically activated by an extracellular protein complex comprised of Collagen and calcium binding EGF domains 1 (CCBE1) protein and the protease A disintegrin and metallopeptidase with thrombospondin type 1 motif 3 (ADAMTS3)."

	* '''Tie1 is required for lymphatic valve and collecting vessel development'''{{#pmid:25576926\|PMID25576926}} "Tie1 is a receptor tyrosine kinase with broad expression in embryonic endothelium. Reduction of Tie1 levels in mouse embryos with a hypomorphic Tie1 allele resulted in abnormal lymphatic patterning and architecture, decreased lymphatic draining efficiency, and ultimately, embryonic demise. ... Our findings reveal a fundamental role for Tie signaling during lymphatic vessel remodeling and valve morphogenesis and implicate it as a candidate gene involved in primary lymphedema."		* '''Tie1 is required for lymphatic valve and collecting vessel development'''{{#pmid:25576926\|PMID25576926}} "Tie1 is a receptor tyrosine kinase with broad expression in embryonic endothelium. Reduction of Tie1 levels in mouse embryos with a hypomorphic Tie1 allele resulted in abnormal lymphatic patterning and architecture, decreased lymphatic draining efficiency, and ultimately, embryonic demise. ... Our findings reveal a fundamental role for Tie signaling during lymphatic vessel remodeling and valve morphogenesis and implicate it as a candidate gene involved in primary lymphedema."

Z8600021 at 00:48, 11 February 2019

2019-02-11T00:48:40Z

← Older revision		Revision as of 11:48, 11 February 2019
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	==Lymph Node Development==		==Lymph Node Development==
			{\|
	[[File:Lymph_node_cartoon_01.jpg\|alt=Lymph node cartoon\|300px]]		\| [[File:Lymph_node_cartoon_01.jpg\|alt=Lymph node cartoon\|300px]]
			\| Lymphatic vasculature drains lymph fluid from the organ tissue space and returns it to the blood vasculature for recirculation. Lymph nodes lie on the path of lymph vessels and these structures monitor and carry out immune surveillance of this fluid for antigens and pathogens, trapping them within the lymph nodes and generating immune responses.

	:'''Links:''' [[Lymph Node Development]]		:'''Links:''' [[Lymph Node Development]]
			\|}

	==T Lymphocyte Development==		==T Lymphocyte Development==

Z8600021 at 21:17, 4 Ocak 2019

2019-01-04T21:17:10Z

← Older revision		Revision as of 08:17, 5 Ocak 2019
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	\| [[File:Mark_Hill.jpg\|90px\|left]] {{Most_Recent_Refs}}		\| [[File:Mark_Hill.jpg\|90px\|left]] {{Most_Recent_Refs}}

	Search term: [http://www.ncbi.nlm.nih.gov/pubmed/?term=Immune+System+Development ''Immune System Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Lymphatic+System+Development ''Lymphatic System Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Thymus+Development ''Thymus Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Spleen+Development ''Spleen Development''] \| \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Lymph+Node+Development ''Lymph Node Development'']		Search term: [http://www.ncbi.nlm.nih.gov/pubmed/?term=Immune+System+Development ''Immune System Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Lymphatic+System+Development ''Lymphatic System Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Thymus+Development ''Thymus Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Spleen+Development ''Spleen Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Lymph+Node+Development ''Lymph Node Development'']

	\|}		\|}

Z8600021 at 21:16, 4 Ocak 2019

2019-01-04T21:16:28Z

← Older revision		Revision as of 08:16, 5 Ocak 2019
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	:'''Links:''' {{gastrointestinal tract}}		:'''Links:''' {{gastrointestinal tract}}

			===Macrophages===

			Macrophages appear in the fetal intestine at 11-12 week {{GA}} and rapidly increase in number during the {{second trimester}} (12 to 22 week {{GA}}). Macrophage development also precedes the appearance of other immune cells (lymphocytes and neutrophils).{{#pmid:19443732\|PMID19443732}}
	==Other Organs==		==Other Organs==

	* '''Liver~~''' -~~ The adult {{liver}} is a lymphoid organ with a predominantly innate immune system. NK cells are abundant in the normal liver (about one-third of intrahepatic lymphocytes), differs from other lymphoid organs and peripheral blood.		===Liver===
			The adult {{liver}} is a lymphoid organ with a predominantly innate immune system. NK cells are abundant in the normal liver (about one-third of intrahepatic lymphocytes), differs from other lymphoid organs and peripheral blood.

Z8600021 at 21:11, 4 Ocak 2019

2019-01-04T21:11:59Z

@@ Line 27: / Line 27: @@
 * '''The Nobel Prize in Physiology or Medicine''' [http://www.nobelprize.org/nobel_prizes/medicine/laureates/2011/ 2011]  Bruce A. Beutler and Jules A. Hoffmann ''for their discoveries concerning the activation of innate immunity'' and the other half to Ralph M. Steinman ''for his discovery of the dendritic cell and its role in adaptive immunity''.
 * '''Regulation of lymphatic-blood vessel separation by endothelial Rac1.'''{{#pmid:19906871|PMID19906871}} "Sprouting angiogenesis and lymphatic-blood vessel segregation both involve the migration of endothelial cells, but the precise migratory molecules that govern the decision of blood vascular endothelial cells to segregate into lymphatic vasculature are unknown."
 * '''The development of intestinal lymphoid tissues at the interface of self and microbiota'''{{#pmid:19741595|PMID19741595}} "(postnatal) Intestinal lymphoid tissues face the challenging task of inducing adaptive immunity to pathogens, yet maintaining homeostasis with the enormous commensal microbiota. To that aim, the ancient partnership between self and flora has resulted in the generation of a unique set of lymphoid tissues capable of constant large-scale reformatting. A first set of lymphoid tissues, the mesenteric lymph nodes and Peyer's patches, are programmed to develop in the sterile environment of the fetus, whereas a second set of lymphoid tissues, the tertiary lymphoid tissues, are induced to form by the microbiota and inflammation."
 * '''Ordering human CD34+CD10-CD19+ pre/pro-B-cell and CD19- common lymphoid progenitor stages in two pro-B-cell development pathways.'''{{#pmid:20231472|PMID20231472}} "Here, we show a similar divergence in human B-cell development pathways between the Pax5(+)TdT(-) pre/pro-B differentiation pathway that gives rise to infant B-lineage leukemias and the early-B pathway."
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 * '''Ontogeny of reticular framework of white pulp and marginal zone in human spleen: immunohistochemical studies of fetal spleens from the 17th to 40th week of gestation.''' {{#pmid:19255788|PMID19255788}} "The reticular framework of the periarteriolar lymphoid sheath (PALS), lymph follicle (LF), and marginal zone (MZ) is thus heterogeneous in the fetal spleen, and the development of the heterogeneity is related to the ontogeny of the PALS, LF, and MZ."
 |}
 == Spleen Development==

Z8600021 at 21:10, 4 Ocak 2019

2019-01-04T21:10:49Z

← Older revision		Revision as of 08:10, 5 Ocak 2019
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	\| [[File:Mark_Hill.jpg\|90px\|left]] {{Most_Recent_Refs}}		\| [[File:Mark_Hill.jpg\|90px\|left]] {{Most_Recent_Refs}}

	Search term: [http://www.ncbi.nlm.nih.gov/pubmed/?term=Immune+System+Development ''Immune System Development'']		Search term: [http://www.ncbi.nlm.nih.gov/pubmed/?term=Immune+System+Development ''Immune System Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Lymphatic+System+Development ''Lymphatic System Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Thymus+Development ''Thymus Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Spleen+Development ''Spleen Development''] \| \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Lymph+Node+Development ''Lymph Node Development'']

	~~<pubmed limit=5>Immune System Development</pubmed>~~
	\|}		\|}
	== Spleen Development==		== Spleen Development==

Z8600021 at 00:40, 9 August 2018

2018-08-09T00:40:09Z

← Older revision		Revision as of 11:40, 9 August 2018
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	===Reviews===		===Reviews===
			{{#pmid:24861898}}

	{{#pmid:21071706}}		{{#pmid:21071706}}

Z8600021 at 22:40, 10 Mayıs 2018

2018-05-10T22:40:22Z

← Older revision		Revision as of 09:40, 11 Mayıs 2018
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	[[File:Stage 22 image 169.jpg\|thumb\|alt=Developing Human Thymus (Carnegie stage 22)\|Developing Human Thymus ([[Carnegie stage 22\|stage 22]])]]		[[File:Stage 22 image 169.jpg\|thumb\|alt=Developing Human Thymus (Carnegie stage 22)\|Developing Human Thymus ([[Carnegie stage 22\|stage 22]])]]
	Development of the immune system will also link to cardiovascular development notes (blood and vessel) and bone marrow development. Two organs which also relate to this system are the thymus and spleen, which have in the past been included in endocrine and gastrointestinal tract development respectively. There are now also movies showing lymphocyte (B and T cells) traffic within adult lymph nodes.		Development of the immune system will also link to cardiovascular development notes ({{blood}} and vessel) and {{bone}} marrow development. Two organs which also relate to this system are the thymus and spleen, which have in the past been included in {{endocrine}} and {{gastrointestinal tract}} development respectively. There are now also movies showing lymphocyte (B and T cells) traffic within adult lymph nodes.

Z8600021 at 00:02, 1 Mayıs 2018

2018-05-01T00:02:05Z

← Older revision		Revision as of 11:02, 1 Mayıs 2018
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	{\| class="prettytable"		{\| class="prettytable"
	\| [[File:Stage_13_image_074.jpg\|300px]]		\| [[File:Stage_13_image_074.jpg\|300px]]
	\| The human spleen arises in week 5 within the [[D#dorsal mesogastrium\|dorsal mesogastrium]] as proliferating [[M#mesenchyme\|mesenchyme]] overlying the dorsal pancreatic endoderm. Cells required for its hemopoietic function arise from the yolk sac wall and near dorsal aorta.		\| The human {{spleen}} arises in [[week 5]] within the [[D#dorsal mesogastrium\|dorsal mesogastrium]] as proliferating [[M#mesenchyme\|mesenchyme]] overlying the dorsal pancreatic endoderm. Cells required for its hemopoietic function arise from the yolk sac wall and near dorsal aorta.

	The spleen generates both red and white cells in the 2nd trimester. Note that many embryonic RBCs remain nucleated.		The spleen generates both red and white cells in the 2nd trimester. Note that many embryonic RBCs remain nucleated.
	\|-		\|-
	\| [[:File:Stage_13_image_074.jpg\|D4]] Dorsal Mesogastrium ([[Carnegie stage ~~13\|stage 13~~)]]		\| [[:File:Stage_13_image_074.jpg\|D4]] Dorsal Mesogastrium (Carnegie stage {{CS13}})]]
	\|		\|
	\|}		\|}
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	:'''Links:''' ~~[[Cardiovascular_System_-_Spleen_Development\|Spleen Development]]~~		:'''Links:''' {{spleen}}
	==Thymus Development==		==Thymus Development==

	{\| class="prettytable"		{\| class="prettytable"
	\| [[File:Stage_22_image_071.jpg\|alt=Embryonic thymus\|300px]]		\| [[File:Stage_22_image_071.jpg\|alt=Embryonic thymus\|300px]]
	\| The thymus has a key role in the development of an effective immune system as well as an endocrine function.		\| The {{thymus}} has a key role in the development of an effective immune system as well as an endocrine function.
	The thymus has two origins for the lymphoid thymocytes and the thymic epithelial cells. The thymic epithelium begins as two flask-shape endodermal diverticula that form from the third pharyngeal pouch and extend lateralward and backward into the surrounding mesoderm and neural crest-derived mesenchyme in front of the ventral aorta.		The thymus has two origins for the lymphoid thymocytes and the thymic epithelial cells. The thymic epithelium begins as two flask-shape endodermal diverticula that form from the third pharyngeal pouch and extend lateralward and backward into the surrounding mesoderm and neural crest-derived mesenchyme in front of the ventral aorta.
	\|-		\|-
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	:'''Links:''' ~~[[Thymus Development]]~~		:'''Links:''' {{thymus}}

	==Lymph Node Development==		==Lymph Node Development==
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	Peyer's patches appear and are continuously formed from 13.5 weeks ({{GA}} 15.5 wk) through to about 36 weeks in the gastrointestinal tract. Then between 15.5 and 20 weeks ({{GA}}17.5 wk to 22 wk) they develop the surface markers of lymphocytes in the mucosal immune system of the gut.{{#pmid:11589311\|PMID11589311}} This developmental change is also occurring within the appendix lymphocyte markers: HLA - DR, CD19 (B cell population), CD9 (pre-B cells), CD3 T lymphocytes, CD4 helper / inducer lymphocytes, the CD8 suppressor / cytotoxic cells and lastly, the CD57 Natural Killer cells.		Peyer's patches appear and are continuously formed from 13.5 weeks ({{GA}} 15.5 wk) through to about 36 weeks in the gastrointestinal tract. Then between 15.5 and 20 weeks ({{GA}}17.5 wk to 22 wk) they develop the surface markers of lymphocytes in the mucosal immune system of the gut.{{#pmid:11589311\|PMID11589311}} This developmental change is also occurring within the appendix lymphocyte markers: HLA - DR, CD19 (B cell population), CD9 (pre-B cells), CD3 T lymphocytes, CD4 helper / inducer lymphocytes, the CD8 suppressor / cytotoxic cells and lastly, the CD57 Natural Killer cells.

			:'''Links:''' {{gastrointestinal tract}}
	==Other Organs==		==Other Organs==

	* '''Liver''' - The adult liver is a lymphoid organ with a predominantly innate immune system. NK cells are abundant in the normal liver (about one-third of intrahepatic lymphocytes), differs from other lymphoid organs and peripheral blood.		* '''Liver''' - The adult {{liver}} is a lymphoid organ with a predominantly innate immune system. NK cells are abundant in the normal liver (about one-third of intrahepatic lymphocytes), differs from other lymphoid organs and peripheral blood.


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	:'''Links:''' ~~[[Placenta Development]]~~ \| ~~[[Normal_Development_-_Milk\|Milk]]~~		:'''Links:''' {{placenta}} \| {{milk}}

	==Additional Images==		==Additional Images==