Structure and Function of the Major Histocompatibility Complex (MHC) Proteins.
When disease associated proteins occur in a cell they are broken into pieces by the cells proteolytic machinery. Cell proteins become attached to antigen fragments and transport them to the surface of the cell, where they are "presented" to the bodies defence mechanisms.
These transport molecules are called the Major Histocompatibility Complex (MHC) proteins. Without these, there would be no presentation of internal or external antigens to the T cells. The importance of MHC proteins is that they allow T cells to distinguish self from non-self. In every cell in your body, antigens are constantly broken up and presented to passing T cells. Without this presentation, other aspects of the immune response cannot occur.
Class I MHC proteins (found on all nucleated cell surfaces) present antigens to cytotoxic T lymphocytes (CTLs) . Most CTLs possess both T-cell receptors (TCR) and CD8 molecules On their surfaces. These TCRs are able to recognize peptides when they are expressed in complexes with MHC Class I molecules. For the TCR to bind a peptide-MHC complex two conditions must be met. Firstly, the TCR must have a structure which allows it to bind the peptide-MHC complex. Secondly, the accessory molecule CD8, must bind to the alpha-3 domain of the MHC Class I molecule. Due to genetic recombination events each CTL expresses a unique TCR which only binds a specific MHC-peptide complex. CTLs which recognize self-peptides (i.e. peptides produced by the normal host body as opposed to a foreign or cancerous cells) are removed in the thymus or tolerized after their release from the thymus. So, if a CTL can bind to a MHC-peptide complex on the cell surface, that cell is producing a peptide which is not native to the host.
The MHC Class II proteins (found only on B lymphocytes, macrophages, and other cells that present antigens to T cells), which primarily present peptides which have been digested from external sources, are needed for T-cell communication with B-cells and macrophages. Class II MHC proteins presenting antigens are detected by a different group of T cells (called T-helper or TH cells) to Class I MHC proteins (which are detected by CTLs cells).
The MHC proteins, and several closely associated with them in the carrying out of their functions, are coded for by loci that are close together within the Human Genome. Major Histocompatibility Complex proteins and their associated molecules are fundamental in the process of antigen presentation. The following pages collect and collate some of the information relating to this process.
Major Histocompatibility Complex is a set of molecules displayed cell surfaces which are responsible for lymphocyte recognition and antigen presentation...
Well, T cells cant able directly bind to the antigen, instead the antigen must be presented to the T cell receptor. So Inorder to do that MHC complex is produced by the host cell or APC (antigen presenting cells) like dendritic cells, macrophages. The antigen will bind to the MHC complex and get exposed on the APC cell surface. There are two types of MHC complex: MHC class I and class II. Class II will found in the APC and present antigen only to T helper cells. whereas the Class I will be produced on the host cell when it is affected some virus or bacteria. These will present to the cytotoxic T cells.
Thank u
http://en.wikipedia.org/wiki/Major_histocompatibility_complex
http://en.wikipedia.org/wiki/Major_histocompatibility_complex
The role is to attempt to the signals of a foreign antigen presented in our body and to regulate the self and non-self status of our biological system, and more, to downregulate the initiation of a molecular disease due to DNA failure.
Structure and Function of the Major Histocompatibility Complex (MHC) Proteins.
When disease associated proteins occur in a cell they are broken into pieces by the cells proteolytic machinery. Cell proteins become attached to antigen fragments and transport them to the surface of the cell, where they are "presented" to the bodies defence mechanisms.
These transport molecules are called the Major Histocompatibility Complex (MHC) proteins. Without these, there would be no presentation of internal or external antigens to the T cells. The importance of MHC proteins is that they allow T cells to distinguish self from non-self. In every cell in your body, antigens are constantly broken up and presented to passing T cells. Without this presentation, other aspects of the immune response cannot occur.
Class I MHC proteins (found on all nucleated cell surfaces) present antigens to cytotoxic T lymphocytes (CTLs) . Most CTLs possess both T-cell receptors (TCR) and CD8 molecules On their surfaces. These TCRs are able to recognize peptides when they are expressed in complexes with MHC Class I molecules. For the TCR to bind a peptide-MHC complex two conditions must be met. Firstly, the TCR must have a structure which allows it to bind the peptide-MHC complex. Secondly, the accessory molecule CD8, must bind to the alpha-3 domain of the MHC Class I molecule. Due to genetic recombination events each CTL expresses a unique TCR which only binds a specific MHC-peptide complex. CTLs which recognize self-peptides (i.e. peptides produced by the normal host body as opposed to a foreign or cancerous cells) are removed in the thymus or tolerized after their release from the thymus. So, if a CTL can bind to a MHC-peptide complex on the cell surface, that cell is producing a peptide which is not native to the host.
The MHC Class II proteins (found only on B lymphocytes, macrophages, and other cells that present antigens to T cells), which primarily present peptides which have been digested from external sources, are needed for T-cell communication with B-cells and macrophages. Class II MHC proteins presenting antigens are detected by a different group of T cells (called T-helper or TH cells) to Class I MHC proteins (which are detected by CTLs cells).
The MHC proteins, and several closely associated with them in the carrying out of their functions, are coded for by loci that are close together within the Human Genome. Major Histocompatibility Complex proteins and their associated molecules are fundamental in the process of antigen presentation. The following pages collect and collate some of the information relating to this process.
Excellent descriptions, but simply here you can see the 3 major categories of MHC roles:
1. antigen presentation to T cells
2. "decoding" for T cells the ("infected") cell type doing the presentation, in order to trigger the right counteraction - see the righ immune response
3. other functions such as the control of body weigth, egg production, internalization of and other interactions with endophins
Last not least the genes class I are belonging to a very polymorphic cluster where lots of silent genes exist - a source of variability and, probably, evolution, in creatures equipped with MHC
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