T cell differentiation - Revision history

Bara at 16:18, 2 July 2012

2012-07-02T16:18:26Z

Rjfrancisrvc: /* Introduction */

2012-05-28T12:16:23Z

Introduction

Rjfrancisrvc: /* Introduction */

2012-05-28T12:15:56Z

Introduction

Rjfrancisrvc: /* TH17 Cells */

2012-05-23T11:11:36Z

TH17 Cells

Rjfrancisrvc at 08:41, 23 May 2012

2012-05-23T08:41:12Z

Rjfrancisrvc: /* Maturation signals */

2012-05-22T15:41:23Z

Maturation signals

Rjfrancisrvc: /* TH17 Cells */

2012-05-22T15:39:44Z

TH17 Cells

Rjfrancisrvc: /* TH17 Cells */

2012-05-22T15:38:57Z

TH17 Cells

Rjfrancisrvc: /* TH1 Cells */

2012-05-18T09:37:05Z

TH1 Cells

Rjfrancisrvc: /* TH17 Cells */

2012-05-18T09:36:08Z

TH17 Cells

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 [[Image:TH1-2.jpg|thumb|right|200px|TH1 and 2 selection is influenced by infection - B. Catchpole, RVC 2008]]
 ==Introduction==
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 <br><br>
 {{Jim Bee 2007}}
 [[Category:Lymphocytes|E]]
 [[Category:Adaptive Immune System|C]]

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 ==Introduction==
 [[T cells|T cells]] are long lived and are involved in '''cell mediated immunity'''. Functionally they are divided by the expression of CD4<sup>+</sup> or CD8<sup>+</sup> markers. CD4<sup>+</sup> T helper cells recognise antigens bound to MHC II complexes and are involved with the control of intracellular and extracellular pathogens; they can interact with CD8<sup>+</sup>, NK and dendritic cells or with B cells. Cytotoxic CD8<sup>+</sup> T cells recognise the MHC I complex and destroy infected or neoplastic cells.
+<br />
 Within the blood and lymphoid organs the majority of T cells are antigen-naive T cells; only a small proportion are memory T cells. Naive T cells have yet to encounter antigen and can only be activated by antigen that is presented by dendritic cells. After initial antigenic activation, naïve T-cells develop into an intermediate stage cell called the T<sub>H</sub>0 cell which can then be activated by any antigen-presenting cell, e.g. Dendritic cells, [[Macrophages|macrophages]] or [[B cells]].
+<br />
 The T<sub>H</sub>0 cells have the capacity to differentiate into T<sub>H</sub>1, T<sub>H</sub>2 cells and a very recently described subtype T<sub>H</sub>17 cells. The type of cell that develops depends on the antigen presenting cell type. [[Macrophages|Macrophages]] cause the T<sub>H</sub>0 cell to develop into a T<sub>H</sub>1 cell induced by IL-12 production following macrophage-antigen interaction. B cells cause the T<sub>H</sub>0 cell to develop into a T<sub>H</sub>2 cell induced by IL-10 production following B cell-antigen interaction. On antigenic stimulation the T<sub>H</sub>1 or T<sub>H</sub>2 cells become activated, undergo clonal expansion and secrete a range of different cytokines. The third most recently described subset, T<sub>H</sub>17, form in the presence of IL-6 and TGF-β which are produced in the prescence of infection, and by either of the Antigen Presenting Cells (APCs). The importance of CD4<sup>+</sup> T<sub>H</sub> cells is very clear in immunity. An example of a disease that targets CD4<sup>+</sup> T cells is the Human Immunodeficieny Viruses (HIV) and Simian Immunodeficieny Viruses (SIV) which, when the CD4<sup>+</sup> T cells are overwhelmed, causes Advanced Immunodeficiency Syndrome (AIDS).
+<br />
 For any one cell the cytokine-secreting activation state is short-lived, lasting between 4 - 40 hours. After this time these cells either die or mature into the long-lived memory cells. The proliferation of [[T cells]] continues until the presentation of antigen ceases.

@@ Line 3: / Line 3: @@
 [[T cells|T cells]] are long lived and are involved in '''cell mediated immunity'''. Functionally they are divided by the expression of CD4<sup>+</sup> or CD8<sup>+</sup> markers. CD4<sup>+</sup> T helper cells recognise antigens bound to MHC II complexes and are involved with the control of intracellular and extracellular pathogens; they can interact with CD8<sup>+</sup>, NK and dendritic cells or with B cells. Cytotoxic CD8<sup>+</sup> T cells recognise the MHC I complex and destroy infected or neoplastic cells.
-Within the blood and lymphoid organs the majority of T cells are antigen-naive T cells; only a small proportion are memory T cells. Naive T cells have yet to encounter antigen and can only be activated by antigen that is presented by dendritic cells. After initial antigenic activation, naïve T-cells develop into an intermediate stage cell called the TH<sub>0</sub> cell which can then be activated by any antigen-presenting cell, e.g. Dendritic cells, [[Macrophages|macrophages]] or [[B cells]].
+Within the blood and lymphoid organs the majority of T cells are antigen-naive T cells; only a small proportion are memory T cells. Naive T cells have yet to encounter antigen and can only be activated by antigen that is presented by dendritic cells. After initial antigenic activation, naïve T-cells develop into an intermediate stage cell called the T<sub>H</sub>0 cell which can then be activated by any antigen-presenting cell, e.g. Dendritic cells, [[Macrophages|macrophages]] or [[B cells]].
-The T<sub>H</sub>0 cells have the capacity to differentiate into T<sub>H</sub>1, T<sub>H</sub>2 cells and a very recently described subtype T<sub>H</sub>17 cells. The type of cell that develops depends on the antigen presenting cell type. [[Macrophages|Macrophages]] cause the T<sub>H</sub>0 cell to develop into a T<sub>H</sub>1 cell induced by IL-12 production following macrophage-antigen interaction. B cells cause the T<sub>H</sub>0 cell to develop into a T<sub>H</sub>2 cell induced by IL-10 production following B cell-antigen interaction. On antigenic stimulation the T<sub>H</sub>1 or T<sub>H</sub>2 cells become activated, undergo clonal expansion and secrete a range of different cytokines. The third most recently described subset, T<sub>H</sub>17, form in the presence of IL-6 and TGF-β which are produced in the prescence of infection, and by either of the Antigen Presenting Cells (APCs).
+The T<sub>H</sub>0 cells have the capacity to differentiate into T<sub>H</sub>1, T<sub>H</sub>2 cells and a very recently described subtype T<sub>H</sub>17 cells. The type of cell that develops depends on the antigen presenting cell type. [[Macrophages|Macrophages]] cause the T<sub>H</sub>0 cell to develop into a T<sub>H</sub>1 cell induced by IL-12 production following macrophage-antigen interaction. B cells cause the T<sub>H</sub>0 cell to develop into a T<sub>H</sub>2 cell induced by IL-10 production following B cell-antigen interaction. On antigenic stimulation the T<sub>H</sub>1 or T<sub>H</sub>2 cells become activated, undergo clonal expansion and secrete a range of different cytokines. The third most recently described subset, T<sub>H</sub>17, form in the presence of IL-6 and TGF-β which are produced in the prescence of infection, and by either of the Antigen Presenting Cells (APCs). The importance of CD4<sup>+</sup> T<sub>H</sub> cells is very clear in immunity. An example of a disease that targets CD4<sup>+</sup> T cells is the Human Immunodeficieny Viruses (HIV) and Simian Immunodeficieny Viruses (SIV) which, when the CD4<sup>+</sup> T cells are overwhelmed, causes Advanced Immunodeficiency Syndrome (AIDS).
 For any one cell the cytokine-secreting activation state is short-lived, lasting between 4 - 40 hours. After this time these cells either die or mature into the long-lived memory cells. The proliferation of [[T cells]] continues until the presentation of antigen ceases.

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 ''Still under investigation''
 <br />
-The T<sub>H</sub>17 cells form when T<sub>H</sub>0 cells are challenged with IL-6 and TGF-β to produce a number of cytokines that enhance the innate immune response <ref>{{citation|initiallast = Metcalfe|initialfirst = T|2last = Korn|2first = D|finallast = Kuchroo|finalfirst = V.K.|year = 2009|jtitle = IL-17 and Th17 Cells
+The T<sub>H</sub>17 cells form when T<sub>H</sub>0 cells are challenged with IL-6 and TGF-β to produce a number of cytokines that enhance the innate immune response <ref>{{citation|initiallast = Korn|initialfirst = T|2last = Bettelli|2first = E|3last = Oukka|3first = M|finallast = Kuchroo|finalfirst = V.K|year = 2009|jtitle = IL-17 and Th17 Cells|jor = Annual Reviews of Immunology|vol = 27|range = 485-517}}</ref>. The [[Cytokines|cytokines]] produced enhance the extravasation and chemotaxis of [[Neutrophils|neutrophils]] to the site of infection, in the aim of combating extracellular bacteria. These cytokines include:
 *IL-17
 *IL-17F

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 TH cells secrete cytokines for only a short period after they have been activated; the range of cytokines that T<sub>H</sub> cells secrete after activation chiefly determines their function. Different T-helper cell subpopulations (T<sub>H</sub>1, T<sub>H</sub>2 and T<sub>H</sub>17 cells) secrete different sets of cytokines.
 <br><br>
 {{Jim Bee 2007}}

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 **Helminths (SEA, ES 62)
 *Endogenous
-**Inflammatory mediators (IL-1/TNF-a, hsp, FcR)
+**Inflammatory mediators (IL-1/TNF&alpha;, hsp, FcR)
 **Immune cells (CD40L, CD47, FasL)
 [[Image:Maturation of Dendritic Cells.jpg|thumb|right|300px|Maturation of Dendritic Cells - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]

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 T<sub>H</sub>1 cells secrete a range of cytokines, including:
-* '''IL-2''', which induces proliferation of both [[Helper_CD4%2B#Helper_CD4.2B|CD4<sup>+</sup>]] and [[Cytotoxic_CD8%2B#Cytotoxic_CD8.2B|CD8<sup>+</sup> T-cells]]. This stimulation of T cell proliferation is the main function of the TH<sub>1</sub> cell.
+* '''IL-2''', which induces proliferation of both [[Helper_CD4%2B#Helper_CD4.2B|CD4<sup>+</sup>]] and [[Cytotoxic_CD8%2B#Cytotoxic_CD8.2B|CD8<sup>+</sup> T-cells]]. This stimulation of T cell proliferation is the main function of the T<sub>H</sub>1 cell.
 * '''Interferon gamma''' ('''IFN&gamma;''') which activates tissue macrophages and is the principal effector mechanism in the defence against intracellular bacteria and parasites such as  Mycobacteria, Brucella, Rickettsia Leishmania, Coccidia, and Babesia. IFN&gamma; activates macrophages and stimulates them to produce enzymes triggering intracellular killing mechanisms - specifically:
 #Superoxide dismutase and myeloperoxidase that produce H<sub>2</sub>O<sub>2</sub> and trigger the "superoxide burst".

@@ Line 66: / Line 66: @@
 *IL-17F
 *IL-6
-*TNF-
+*TNFα
 *IL-21
 *IL-22
 *IL-23
 Importantly they do not produce:
-IFN normally associated with T<sub>H</sub>1 cells
+*IFNγ normally associated with T<sub>H</sub>1 cells
-IL-4 normally associated with T<sub>H</sub>2 cells
+*IL-4 normally associated with T<sub>H</sub>2 cells
 ==Cytotoxic T-Cells==