MHC markers or Major Histo-compatibility Complex, are proteins expressed on the surface of a cell. They are used primarily in the recognition of pathogens in immune responses.
We can break MHC markers up into 2 types, MHC 1 and MHC 2
MHC 1
MHC 1 markers are present on every single Nucleated cell in your body. Essentially every cell except mature red blood cells, will have an MHC 1 marker.
These markers are extremely important in the recognition of viral or bacteria infected cells or malfunctioning cells.
Lets say, a cell becomes Infected by a virus. It will begin producing viral pieces. These pieces are then presented on it’s MHC marker.
Once the cell is damaged or infected it will present abnormal proteins on it’s surface.
Natural killer (NK) cells will come over, read the MHC 1 marker, and kill the cell.
The video to the right shows a NK cell (red) killing tumour cells. Once the tumour cell is killed it become blue.
MHC 2
MHC 2 markers are slightly different. Unlike MHC 1 they are only found on antigen presenting cells, like Macrophages and Dendritic cells.
MHC 2 markers also present antigens, however these cells engulf the pathogen, break it up and present the antigen pieces on their MHC 2 markers
Once presented on their MHC 2, Helper T cells can bind and recognise the antigen. Th cells have a TCR (T cell receptor) which binds to the MHC marker
As always, on the correct T cell can bind to the specific antigen.
The T-cell then replicate into Th, Tc and Tm cells and call other immune cells to fight.
Similarly when T cells get involved, Cytotoxic T cells (Tc) will bind to the MHC1 marker and kill the cell.
As with all T cells, they require the correct antigen to become activated.
The video to the left shows a Dendritic cell presenting an antigen to a T cell.
Once activated the T cell it becomes a bright green.
