Effector-Memory-T-Cells, residental

Resident effector memory T cells (Trm cells) are a specialized subgroup of memory T cells that remain permanently in tissues and enable a rapid immune response against infections or tumor cells.

Properties of Trm cells:

Tissue residence:

• Trm cells do not circulate in the blood, but remain permanently in peripheral tissues such as skin, lung, intestine or brain.
• Trm cells express specific adhesion molecules (e.g. CD69 and CD103) that promote their anchoring in the tissue.

Rapid immune response:

• Trm cells can immediately release cytokines (e.g. IFN-γ, TNF-α) and activate other immune cells upon renewed contact with pathogens.
• Trm cells have a high effector function, similar to classic effector cells.

Protection against infections and tumors:

• Trm cells play a key role in the defense against viral and bacterial infections.
• Trm cells are also involved in immune surveillance against tumor cells.

Long-term memory:

• Although Trm cells remain in the tissue, they can survive for long periods of time and protect the body from re-infection.

Importance for medicine:

• Immunotherapy: Trm cells are being researched as a target for vaccination strategies and cancer therapies.
• Autoimmune diseases: Misdirected Trm cells can be involved in chronic autoimmunological inflammations (e.g. psoriasis or multiple sclerosis).
• Mycosis fungoides: The tumor cells of mycosis fungoides are identified as skin-resident effector memory T cells of clonal origin. In contrast, Sézary cells are referred to as "central memory T cells" with expression of the lymph node homing molecules CCR7 and L-selectin.