Changes

==Regulatory T Cells==

==Regulatory T Cells==

A number of cell populations identified during studies on autoimmunity and organ transplantation have shown the capacity to suppress responses to self-antigen and regulate rejection. Although once considered a tentative theory, this form of tolerance is now considered a major mechanism in the protection of host tissue from immune attack.  

A number of cell populations identified during studies on autoimmunity and organ transplantation have shown the capacity to suppress responses to self-antigen and therefore can be utelised to regulate rejection. Although once considered a tentative theory, this form of tolerance is now considered a major mechanism in the protection of host tissue from immune attack.  

[[Image:T reg cells.JPG|thumb|right|150px|Regulatory T cells- copyright Brian Catchpole]]

[[Image:T reg cells.JPG|thumb|right|200px|Regulatory T cells- copyright Brian Catchpole]]

* Known as '''regulatory T cells''', these CD4+ cells are antigen-specific

 

* Currently thought to develop in the thymus

Known as '''regulatory T cells''', CD4+ cells which are antigen-specific are currently thought to develop in the thymus. They usually release inhibitory cytokines, e.g. IL-4, IL-10 and TGF-beta and when their TCRs bind to an antigen, they do not proliferate themselves but suppress the proliferation of other ''naive'' T cells that would normally respond to that antigen.

* They usually release inhibitory cytokines, e.g. IL-4, IL-10 and TGF-beta

The mechanism of suppression is dependent on CTLA-4 on the regulatory T cell binding with B7 on the target T cell and then both cells binding the same antigen.

* When their TCRs bind to an antigen, they do not proliferate themselves but suppress the proliferation of other ''naive'' T cells responding to that antigen

 

* Mechanism of suppression is dependent on:

Regulatory T cells are unique in their use of a transcription repressor known as FoxP3 which is encoded by a gene on the X chromosome; rare deficiencies in FoxP3 are characterised by autoimmunity, primarily towards gut tissue, the thyroid, pancreative beta-cells and the skin. Sufferers are unable to produce regulatory T cells and the only known treatment is a bone marrow transplant from a MHC-identical sibling.

** CTLA-4 on the regulatory T cell binding with B7 on the target T cell

* Both cells binding the same antigen

* Regulatory T cells are unique in their use of a transcription repressor known as FoxP3  

** Encoded by a gene on the X chromosome, rare deficiencies in FoxP3 are characterised by autoimmunity, primarily towards gut tissue, the thyroid, pancreative beta-cells and the skin. Sufferers are unable to produce regulatory T cells and the only known treatment is a bone marrow transplant from a MHC-identical sibling.

==Test yourself with the Immunology Flashcards==

==Test yourself with the Immunology Flashcards==