T-Lymphocytes

T-lymphocytes originate in the bone marrow and mature in the thymus. T-lymphocytes circulate in the blood and lymph system, they may also be found in tissues. They recognise antigens through a unique surface receptor called the T Cell Receptor (TCR).

T-lymphocytes promote an immune response when they recognise an antigen that is presented by another cell such as a dendritic cell, macrophage or other body cells that has become infected. T-lymphocytes randomly bind to antigens presented by these cells until they encounter the antigen they specifically respond to. Once this happens a process called clonal expansion occurs, with the originally activated T-lymphocyte producing multiple copies of itself, known as clones. These clones circulate throughout the body looking for signs of infection or inflammation and carry out a range of different roles within the immune response.

3D rendering of a T-lymphocyte Lymphocytes are characterised by a single large nucleus, shown here in orange in this 3D rendering of a T-lymphocyte.

Source: Blausen Medical (CC)

Some T-lymphocytes (CD4+) help B-lymphocytes produce antibodies to neutralise a threat, while others (CD8+) can directly kill cells that have become infected or cancerous. Regulatory T-lymphocytes play an important role in preventing the body's immune response from attacking itself. Th17 lymphocytes play an important role in the defence against fungal infections.

Cells

Tissues

Soluble Mediators

Pathogens

Vaccination