All T-cells have CD3 receptor complexes and various other CD antigens. CD8 antigens are found on TC-cells and TS-cells. CD8 containing cells respond to antigens displayed on Class I MHC proteins. CD4 antigens are found on TH-cells, and respond to antigens displayed on MHC II proteins. CD4 and CD8 markers are bound to the CD3 complex on the T-cell surface. Activation does not usually occur until the T-cell encounters and recognizes (binds) a second antigen of the same type. The “double-signature” is a double-check before destruction.
There are two types of cells that carry CD8 antigens – cytotoxic T-cells and suppressor T-cells.
