MHC – Class 1 Molecule
Major Histocompatibility Complex (MHC) Class 1 molecules are present in every mammalian species. These molecules play a very important role in the survival of the cell.
So all healthy nucleated cells express MHC Class 1 Molecules in their surface and also exhibit a peptide fragment which is basically the protein of the body.
So if the peptide has the protein of the body the cell is safe. If not it is destroyed (Apoptosis) by cytotoxic T cell lymphocytes (CD8+ T Cells) by releasing Granzymes, Perforins, FAS and FASL. On an average a single T cell can kill 50-100 cells before it becomes old and loses it power and gets swallowed by Macrophages. So very important to know your T Cell counts.
There are only 2 situations that would cause the cell to display a reduced expression of MHC 1 molecule.
- Viral infection
In the above situation the virus in order to protect itself from the attack of the T cell it suppresses the expression of the MHC 1. So when the T cell looks at it it is not able to identify it as an infected cell.
So in this case only Natural Killer cells (NK) can detect this viral infected cell and start to attack them.
So in the case of cancer caused due to virus the goal will be to increase the NK cell count so that they can start to attack and kill the infected cells.