Mucosa Associated Lymphoid Tissue 39)Explain the differences between the organiz
ID: 260244 • Letter: M
Question
Mucosa Associated Lymphoid Tissue 39)Explain the differences between the organized mucosa associated lymphoid tissues (MALT) found along the gastrointestinal tract. 40)Explain how dendritic cells in mucosa associated lymphoid tissues (MALT) uptake antigens? Explain differences based on the type of GALT 41)Explain the molecular mechanisms behind the differential homing observed between naive and effector T cells both in a classical lymph node and in mucosal-associated lymphoid tissues 42)What are Intraepithelial lymphocytes? And where are they distributed? What drive the specific homing of these particular population of lymphocytes? 43)What are the roles of the following chemokynes: CCL.21, CCL18, CCI25 and CCL.28? 44)Define: GALT, NALT and BALT with the context of lymphoid tissues. 45)Explain the immunological characteristics of Lamina Propia. 46) Define and explain the difference between Combinatorial and Junctional diversityExplanation / Answer
39 - Differences between the organized mucosa associated lympjoid tissue found along the gastrointestinal tract.
Diffuse, unencapsulated bundles of lymphatic cells.
This kind of lymphatic tissue consists of lymphocytes and macrophages associated with a reticular fiber network.
It occurs in the lamina propria (middle layer) of the mucus membranes (mucosae) that line the respiratory and gastrointestinal tracts.
Discrete, unencapsulated bundles of lymphatic cells, called lymphatic nodules (follicles).
These bundles have clear boundaries that separate them from neighboring cells. Nodules occur within the lamina propria of the mucus membranes that line the gastrointestinal, respiratory, reproductive, and urinary tracts.
They are referred to as mucosa?associated lymphoid tissue (MALT).
The nodules contain lymphocytes and macrophages that protect against bacteria and other pathogens that may enter these passages with food, air, or urine.
Nodules occur as solitary nodules, or they cluster as patches or aggregates. Here are the major clusters of nodules:
Peyer's patches are clusters of lymphatic nodules that occur in the mucosa that lines the ileum of the small intestine.
40 - Dendritic cells in mucosa associated lymphoid tissue uptake antiges : differences based on the type of GALT.
Dendritic cells are a type of antigen-presenting cells which are located in the tissues that have contact with the external environment, for example skin, lungs, nose, stomach and intestines etc.
In mammalian immune system, the dendritic cells play an important role to process antigen material on the cell surface and present them to the T-cell.
Dendritic cell models are used on the research of immunotherapy.
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41 - The molecular mechnism behing the differential homing observed between native and effector T cells both in a classical lymph node and in mucosal-associated lymphpid tissues.
T lymphocytes lacking the lymph node–homing receptors L-selectin and CCR7 do not migrate to lymph nodes in the steady state.
That lymph nodes draining sites of mature dendritic cells or adjuvant inoculation recruited L-selectin-negative CCR7? effector and memory CD8+ T cells.
This recruitment required CXCR3 expression on T cells and occurred through high endothelial venules in concert with lumenal expression of the CXCR3 ligand CXCL9.
In reactive lymph nodes, recruited T cells established stable interactions with and killed antigen-bearing dendritic cells, limiting the ability of these dendritic cells to activate naive CD4+ and CD8+ T cells.
The inducible recruitment of blood-borne effector and memory T cells to lymph nodes may represent a mechanism for terminating primary and limiting secondary immune responses.
42 - Intraepithelial lymphocytes :
Intraepithelial lymphocytes (IEL) are lymphocytes found in the epithelial layer of mammalian mucosal linings, such as the gastrointestinal (GI) tract and reproductive tract.
However, unlike other T cells, IELs do not need priming.
Upon encountering antigens, they immediately release cytokines and cause killing of infected target cells.
In the GI tract, they are components of gut-associated lymphoid tissue (GALT)
An elevated IEL population, as determined by biopsy, typically indicates ongoing inflammation within the mucosa. In diseases such as celiac sprue, IEL elevation throughout the small intestine is one of many specific markers.
Alternatively, elevated IEL populations can be a marker for developing neoplasia in the tissue such as found in cervical and prostate cancers, as well as some colorectal cancers, particularly those associated with Lynch syndrome.
IELs themselves can, when chronically activated, undergo mutation that can lead to lymphoma.
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