T cells: Difference between revisions
No edit summary |
No edit summary |
||
| (One intermediate revision by one other user not shown) | |||
| Line 1: | Line 1: | ||
T-cells or T-lymphocytes are a group of [[Lymphocytes|lymphocytes]] involved in specific immune response, specifically antigen-specific cellular interactions. There are two main subsets; [[Cytotoxic T-cells|Cytotoxic T-cells]] and [[Helper T-cells|Helper T-cells]], Helper T-cells are further divided into inflammatory ([[TH1|TH1]]) and ([[TH2|TH2]]) Helper cells which assist [[B-cells|B-cells]] by forming [[Antibody|antibodies]]. T-cells are formed from bone marrow stem cells that undergo maturation in the [[Thymus|Thymus]] | T-cells or T-lymphocytes are a group of [[Lymphocytes|lymphocytes]] involved in specific immune response, specifically antigen-specific cellular interactions. There are two main subsets; [[Cytotoxic T-cells|Cytotoxic T-cells]] and [[Helper T-cells|Helper T-cells]], Helper T-cells are further divided into inflammatory ([[TH1|TH1]]) and ([[TH2|TH2]]) Helper cells which assist [[B-cells|B-cells]] by forming [[Antibody|antibodies]]. Cytotoxic T-cells are also known as CD8+ T cells, and Helper T-cells are also known as CD4+ T cells. T-cells are formed from bone marrow stem cells that undergo maturation in the [[Thymus|Thymus]]<ref>Michael Madigan, John Martinko, David Stahl, David Clark. (2012) Brock Biology of Microorganisms, Thirteenth Edition, San Francisco: Pearson. 246-249</ref>. | ||
Individual T cells are able to recognise only certain antigens, discriminating between antigens using protein molecules on the cell surface called receptors. The receptor and the antigen fit together like a lock and a key only when their shapes match perfectly. The number and specificity of T cell receptors appear to be determined by the cell’s genes <ref>http://www.nationalmssociety.org/What-is-MS/Definition-of-MS/T-cells</ref>. | Individual T cells are able to recognise only certain antigens, discriminating between antigens using protein molecules on the cell surface called receptors. The receptor and the antigen fit together like a lock and a key only when their shapes match perfectly. The number and specificity of T cell receptors appear to be determined by the cell’s genes<ref>http://www.nationalmssociety.org/What-is-MS/Definition-of-MS/T-cells</ref>. | ||
Before T cells have encountered an antigen, they are known as naive T cells and they have a low affinity for Interleukin-2 (IL-2). Once they recognise an antigen they become activated and once activated they have a high affinity for IL-2 which leads to lots of IL-2 binding which causes proliferation of T cells (binding of IL-2 causes T cells to begin the cell cycle) | Before T cells have encountered an antigen, they are known as naive T cells and they have a low affinity for Interleukin-2 (IL-2). Naive T cells enter the [[Lymph_node|lymph node]] from blood via high endothelial venules (HEV), to move to a T cell area rich in [[Dendritic_cells|dendritic cells]] and [[Macrophages|macrophages]] ([[Antigen_presenting_cells|APC]]). [[Antigen_presenting_cells|APC]] present specific antigens to the T cell, and deliver other activation signals (e.g [[Cytokines|cytokines]]). Once they recognise an antigen they become activated and once activated they have a high affinity for IL-2 which leads to lots of IL-2 binding which causes a proliferation of T cells (binding of IL-2 causes T cells to begin the cell cycle)<ref>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267244/</ref>. T cells which are not activated (i.e. they did not encounter any [[Antigen|antigen]] or [[MHC_Molecules|MHC]]), leave the lymph node via cortical sinuses into the lymphatics to re-enter cirulation. | ||
Activation of T cells by antigen recognition also causes them to differentiate into 3 different types of T cells. CD8 T cells differentiate into Cytotoxic T cells and CD4 T Cells differentiate into CD4 | Activation of T cells by antigen recognition also causes them to differentiate into 3 different types of T cells. CD8 T cells differentiate into Cytotoxic T cells and CD4 T Cells differentiate into CD4 TH1 and CD4 TH2 cells<ref name="Janeway's Immunology 5th edition">https://www.ncbi.nlm.nih.gov/books/NBK10762/</ref>. | ||
CD4+ T cells recognise peptides bound to MHC class II complexes bound on the cell surface, whereas CD8+ T cells recognise peptides bound to MHC class I complexes bound to the cell surface. | CD4+ T cells recognise peptides bound to MHC class II complexes bound on the cell surface, whereas CD8+ T cells recognise peptides bound to MHC class I complexes bound to the cell surface. | ||
=== Referneces === | === Referneces === | ||
<references /> | <references /> | ||
Latest revision as of 13:39, 18 October 2018
T-cells or T-lymphocytes are a group of lymphocytes involved in specific immune response, specifically antigen-specific cellular interactions. There are two main subsets; Cytotoxic T-cells and Helper T-cells, Helper T-cells are further divided into inflammatory (TH1) and (TH2) Helper cells which assist B-cells by forming antibodies. Cytotoxic T-cells are also known as CD8+ T cells, and Helper T-cells are also known as CD4+ T cells. T-cells are formed from bone marrow stem cells that undergo maturation in the Thymus[1].
Individual T cells are able to recognise only certain antigens, discriminating between antigens using protein molecules on the cell surface called receptors. The receptor and the antigen fit together like a lock and a key only when their shapes match perfectly. The number and specificity of T cell receptors appear to be determined by the cell’s genes[2].
Before T cells have encountered an antigen, they are known as naive T cells and they have a low affinity for Interleukin-2 (IL-2). Naive T cells enter the lymph node from blood via high endothelial venules (HEV), to move to a T cell area rich in dendritic cells and macrophages (APC). APC present specific antigens to the T cell, and deliver other activation signals (e.g cytokines). Once they recognise an antigen they become activated and once activated they have a high affinity for IL-2 which leads to lots of IL-2 binding which causes a proliferation of T cells (binding of IL-2 causes T cells to begin the cell cycle)[3]. T cells which are not activated (i.e. they did not encounter any antigen or MHC), leave the lymph node via cortical sinuses into the lymphatics to re-enter cirulation.
Activation of T cells by antigen recognition also causes them to differentiate into 3 different types of T cells. CD8 T cells differentiate into Cytotoxic T cells and CD4 T Cells differentiate into CD4 TH1 and CD4 TH2 cells[4].
CD4+ T cells recognise peptides bound to MHC class II complexes bound on the cell surface, whereas CD8+ T cells recognise peptides bound to MHC class I complexes bound to the cell surface.
Referneces
- ↑ Michael Madigan, John Martinko, David Stahl, David Clark. (2012) Brock Biology of Microorganisms, Thirteenth Edition, San Francisco: Pearson. 246-249
- ↑ http://www.nationalmssociety.org/What-is-MS/Definition-of-MS/T-cells
- ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267244/
- ↑ https://www.ncbi.nlm.nih.gov/books/NBK10762/