T cells - Revision history

Bara at 17:04, 2 July 2012

2012-07-02T17:04:20Z

Rjfrancisrvc: /* γδ cells */

2012-05-24T09:57:25Z

γδ cells

Rjfrancisrvc: /* Cytotoxic CD8+ */

2012-05-24T09:56:55Z

Cytotoxic CD8+

Rjfrancisrvc: /* Helper CD4+ */

2012-05-17T11:05:38Z

Helper CD4+

Rjfrancisrvc at 11:06, 16 May 2012

2012-05-16T11:06:04Z

Rjfrancisrvc at 11:05, 16 May 2012

2012-05-16T11:05:39Z

Rjfrancisrvc: /* Helper CD4+ */

2012-05-16T11:02:15Z

Helper CD4+

Rjfrancisrvc: /* Helper CD4+ */

2012-05-16T11:02:04Z

Helper CD4+

Rjfrancisrvc: /* Cytotoxic CD8+ */

2012-05-16T10:44:54Z

Cytotoxic CD8+

Rjfrancisrvc: /* Cytotoxic CD8+ */

2012-05-16T10:44:10Z

Cytotoxic CD8+

@@ Line 1: / Line 1: @@
 [[Image:TCR2.jpg|thumb|right|300px|T-cell receptor binds antigen fragments presented by MHC on the cell surface - B. Catchpole, RVC 2008]]
 Also known as '''T lymphocytes'''<br />
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 <br><br>
 {{Jim Bee 2007}}
 [[Category:Lymphocytes|D]]

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 *One with restricted antigen binding, that act as first line defence against invading organisms and recognises antigens bound to MHC I complex
 *The other subset doesn’t require the MHC complex and this subset has two further divisions
-** One producing cytokines and chemokines  (TH<sub>1</sub> and TH<sub>2</sub>)
+** One producing cytokines and chemokines  (T<sub>H</sub>1 and T<sub>H</sub>2)
 **The other having cytotoxic effects.</p>
 <br><br>
 {{Jim Bee 2007}}
 [[Category:Lymphocytes|D]]

@@ Line 28: / Line 28: @@
 **Perforins are structurally related to [[Complement#Membrane Attack Complex|complement factor C9]]
 **Granzymes are proteolytic enzymes that target cell nucleases and cause apoptosis
-In both cases direct contact is required between the T cell and target cell, and cell killing can take several minutes.</p><p> Cytotoxic T cells secrete a pattern of cytokines similar to that of TH<sub>1</sub> cells i.e. IFN-γ but not IL-2. IFN-γ shifts the balance of the immune response in favour of TH<sub>1</sub> cells giving an increased level of T cell proliferation. The initiation of the immune response via cytotoxic T cells leads to the selective proliferation of cytotoxic T cells enhancing the main mechanism of killing infected cells.</p>
+In both cases direct contact is required between the T cell and target cell, and cell killing can take several minutes.</p><p> Cytotoxic T cells secrete a pattern of cytokines similar to that of T<sub>H</sub>1 cells i.e. IFN-γ but not IL-2. IFN-γ shifts the balance of the immune response in favour of TH<sub>1</sub> cells giving an increased level of T cell proliferation. The initiation of the immune response via cytotoxic T cells leads to the selective proliferation of cytotoxic T cells enhancing the main mechanism of killing infected cells.</p>
 ==γδ cells==

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 ==Helper CD4<sup>+</sup>==
-<p>These T cells express the marker CD4 and are categorised into three groups, TH<sub>1</sub> and TH<sub>2</sub>, with a third lineage, TH<sub>17</sub> being recently described. These lineages are distinguished by the cytokines they produce. T helper cells recognise antigens bound to MHC II complexes.
+<p>These T cells express the marker CD4 and are categorised into three groups, T<sub>H</sub>1 and T<sub>H</sub>2, with a third lineage, T<sub>H</sub>17 being recently described. These lineages are distinguished by the cytokines they produce. T helper cells recognise antigens bound to MHC II complexes.
-*TH<sub>1</sub> cells produce IL-2, IFN-γ and TNF-α
+*T<sub>H</sub>1 cells produce IL-2, IFN-γ and TNF-α
-*TH<sub>2</sub> cells produce IL-4, IL-5, IL-10 and IL-13
+*T<sub>H</sub>2 cells produce IL-4, IL-5, IL-10 and IL-13
-*TH<sub>17</sub> cells produce IL-17, IL-17F, IL-21
+*T<sub>H</sub>17 cells produce IL-17, IL-17F, IL-21
-TH<sub>1</sub> cells interact with CD8<sup>+</sup>, NK and dendritic cells and TH<sub>2</sub> cells interact with B cells. TH<sub>1</sub> cells are involved with the control of intracellular pathogens and TH<sub>2</sub> cells extracellular pathogens. IL-2 produced by TH<sub>1</sub> cells stimulates further proliferation of CD4<sup>+</sup> cells. TH<sub>17</sub> cells are produced to enhance innate immunity, with the cytokines produced increasing the extravasation of neutrophils.</p>
+T<sub>H</sub>1 cells interact with CD8<sup>+</sup>, NK and dendritic cells and T<sub>H</sub>2 cells interact with B cells. T<sub>H</sub>1 cells are involved with the control of intracellular pathogens and T<sub>H</sub>2 cells extracellular pathogens. IL-2 produced by T<sub>H</sub>1 cells stimulates further proliferation of CD4<sup>+</sup> cells. T<sub>H</sub>17 cells are produced to enhance innate immunity, with the cytokines produced increasing the extravasation of neutrophils.</p>
-<p>TH<sub>0</sub> populations are CD4<sup>+</sup> cells that have yet to differentiate into TH<sub>1</sub>, TH<sub>2</sub> or TH<sub>17</sub> cells and they secrete IL-2, IL-4, IL-5, IFN-γ. In the presence of IL-4 they develop into TH<sub>2</sub> cells while in the presence of IL-2 they develop into TH<sub>1</sub> cells. In the abscence of IL-2 TH<sub>1</sub> cells will change into TH<sub>2</sub> cells. TH<sub>17</sub> cells develop in the presence of TGF-β and IL-6 and can further develop into TH<sub>1</sub> cells depending on various conditions. </p>
+<p>T<sub>H</sub>0 populations are CD4<sup>+</sup> cells that have yet to differentiate into T<sub>H</sub>1, T<sub>H</sub>2 or T<sub>H</sub>17 cells and they secrete IL-2, IL-4, IL-5, IFN-γ. In the presence of IL-4 they develop into T<sub>H</sub>2 cells while in the presence of IL-2 they develop into T<sub>H</sub>1 cells. In the abscence of IL-2 T<sub>H</sub>1 cells will change into T<sub>H</sub>2 cells. T<sub>H</sub>17 cells develop in the presence of TGF-β and IL-6 and can further develop into T<sub>H</sub>1 cells depending on various conditions. </p>
-<p>TH<sub>1</sub> cells have two populations; one that secretes IFN-γ and is short lived, and the other that doesn’t secrete IFN-γ and is long lived. The cells that do not secrete IFN-γ are termed '''memory T cells'''</p>
+<p>T<sub>H</sub>1 cells have two populations; one that secretes IFN-γ and is short lived, and the other that doesn’t secrete IFN-γ and is long lived. The cells that do not secrete IFN-γ are termed '''memory T cells'''</p>
 <p> T cell differentiation is a field of continual change, with discoveries made on a regular basis. </p>

@@ Line 1: / Line 1: @@
 [[Image:TCR2.jpg|thumb|right|300px|T-cell receptor binds antigen fragments presented by MHC on the cell surface - B. Catchpole, RVC 2008]]
-Also known as '''T lymphocytes'''
+Also known as '''T lymphocytes'''<br />
 ''See also: [[T cell differentiation|T cell differentiation]]
 ==Introduction==
 <p>T cells are so named as they differentiate in the [[Thymus - Anatomy & Physiology|thymus]]. They are long lived and are involved in '''cell mediated immunity'''. They represent 60-80% of the circulating lymphocytes and all express the markers CD2, CD3 and CD7 as well as having T cell receptors (TCR). Each T cell has 30,000 TCRs each of which is identical and recognises antigens and major histocompatability complex (MHC) II.</p><p>Functionally they are divided into three subsets that are distinguished by the presence or absence of CD4 or CD8 markers. CD4 and CD8 cells have α/β antigen receptors while the γδ cells have the γ/δ antigens receptors.</p>

@@ Line 18: / Line 18: @@
 <p>TH<sub>0</sub> populations are CD4<sup>+</sup> cells that have yet to differentiate into TH<sub>1</sub>, TH<sub>2</sub> or TH<sub>17</sub> cells and they secrete IL-2, IL-4, IL-5, IFN-γ. In the presence of IL-4 they develop into TH<sub>2</sub> cells while in the presence of IL-2 they develop into TH<sub>1</sub> cells. In the abscence of IL-2 TH<sub>1</sub> cells will change into TH<sub>2</sub> cells. TH<sub>17</sub> cells develop in the presence of TGF-β and IL-6 and can further develop into TH<sub>1</sub> cells depending on various conditions. </p>
 <p>TH<sub>1</sub> cells have two populations; one that secretes IFN-γ and is short lived, and the other that doesn’t secrete IFN-γ and is long lived. The cells that do not secrete IFN-γ are termed '''memory T cells'''</p>
-<p> T cell differentiation is a field of continual change, with many exciting discoveries made on a regular basis. </p>
+<p> T cell differentiation is a field of continual change, with many discoveries made on a regular basis. </p>
 ==Cytotoxic CD8<sup>+</sup>==

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 *One pathway uses the CD95 (death receptor) which  triggers apoptosis in the target cell (usually other T cells)
 *The other pathway uses perforins and granzymes which form pores in the target cell membrane causing cell lysis
-**Perforins are structurally related to [[Complement#MAC|complement factor C9]]
+**Perforins are structurally related to [[Complement#Membrane Attack Complex|complement factor C9]]
 **Granzymes are proteolytic enzymes that target cell nucleases and cause apoptosis
 In both cases direct contact is required between the T cell and target cell, and cell killing can take several minutes.</p><p> Cytotoxic T cells secrete a pattern of cytokines similar to that of TH<sub>1</sub> cells i.e. IFN-γ but not IL-2. IFN-γ shifts the balance of the immune response in favour of TH<sub>1</sub> cells giving an increased level of T cell proliferation. The initiation of the immune response via cytotoxic T cells leads to the selective proliferation of cytotoxic T cells enhancing the main mechanism of killing infected cells.</p>