Changes

Also known as '''T lymphocytes

Also known as '''T lymphocytes

==Introduction==

==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 MHC II.</p><p>Functionally they are divided into three subsets that are distinguished by 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>

<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 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>

* T-cell receptors are the antigen-specific receptors for T-lymphocytes

 

* T-cell receptors are a combination of either &alpha;&beta; chains or &gamma;&delta; chains

** One T-cell will express either &alpha;&beta; OR &gamma;&delta; TCR

T-cell receptors are the antigen-specific receptors for T-lymphocytes, and are a combination of either &alpha/&beta chains or &gamma/&delta chains; one T-cell will express either &alpha/&beta or &gamma/&delta TCRs. The antigen-binding site of the TCR is produced by a combination of the V domains of the relevant chain. Like antibody, the specificity of the TCR is determined by the '''amino acid composition of the variable domains'''.

* The antigen-binding site of the TCR is produced by a combination of the V domains of either 1&alpha; and 1&beta; chain or 1&gamma; and 1&delta;chain

 

** Like antibody, the specificity of TCR is determined by the '''amino acid composition of the variable domains'''

TCRs are linked to the cell membrane; structurally, they look like a single arm of an antibody molecule consisting of a distal domain and a membrane proximal constant domain

* TCR are '''always''' linked to the cell membrane

* Like antibody, TCR consist of a distal domain and a membrane proximal constant domain

[[Image:T Cell diagram 2.jpg|thumb|right|300px|T Cell - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]

[[Image:T Cell diagram 2.jpg|thumb|right|300px|T Cell - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]