CD8 Count

On 19 August, 2011, in HIV & AIDS FAQ, Resource, by Cindy Pivacic

The CD8 protein comes secondary to the CD4 protein in the story of HIV infection, but CD8 and CD4 are quite closely related in that they are cell surface proteins found predominantly on T cells, and they both bind to HLA protein on other cells.
CD8 is ordinarily found on the surface of killer T cells (as opposed to CD4, ordinarily found on the surface of helper T cells). CD8 binds to HLA class I on some other cell – which, as the diagram below shows, allows the T cell receptor protein to dock to HLA-I and check the antigen (“Ag”) which HLA is presenting.

If the shape of the T cell receptor matches the antigen which is being presented, then a sequence of signals is triggered inside the T cell which causes it to kill the cell which it’s attached to (if it’s a killer T cell) or induce others to kill it (if it’s a helper T cell).

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