T cells

These are white blood cells with important roles in the immune system. They are involved in eradicating and providing long-term protection against infections and cancer (and also have the potential to damage healthy tissues in the body if not targeted and regulated appropriately). Cytotoxic T cells kill cells that are infected (e.g. with viruses) or have become tumour cells. They can sometimes also “cure” cells of infection without destroying them. Most cytotoxic T cells express the marker CD8, but some CD4+ T cells also have cytotoxic activity.

• Helper T cells send signals that tell other immune cells how to fight off the invaders, and support their functions. Most helper T cells express the marker CD4.
• Regulatory T cells control the activity of other cells in the immune system to limit damage to healthy tissues.
• Naïve T cells are T cells that have not yet been activated and differentiated into more mature T cells.
• Memory T cells are antigen-specific T cells that remain long-term after an infection has been removed. These cells allow the immune system to rapidly and effectively respond to encounters with the same invader.