# T cell

Source: https://onco.cc/terms/t-cell/  
OnCo record `t-cell` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The immune system's trained assassins. Each T cell recognises one specific target displayed on a cell's surface and, if the cell is infected or cancerous, kills it. Most immunotherapy is about unleashing them.

## Summary

T cells mature in the thymus and use a receptor (TCR) to inspect peptide fragments held in HLA molecules on other cells; cytotoxic CD8 T cells kill, CD4 helper cells coordinate, and regulatory T cells damp the response down. Tumours evade them by switching on checkpoints such as PD-L1, which exhausts the T cells that reach them, and by losing HLA so there is nothing to inspect. Checkpoint inhibitors reinvigorate exhausted T cells; CAR-T and TCR-T engineer a patient's own T cells with a new targeting receptor; bispecific T-cell engagers grab a T cell with one arm and a tumour cell with the other; and tumour-infiltrating lymphocyte (TIL) therapy expands the T cells already inside a tumour.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: T cells; T-cell; T-cells; T lymphocyte; T lymphocytes; cytotoxic T cell; cytotoxic T cells; CD8 T cell; CD8 T cells; CD8+ T cell; CD8+ T cells; CD8+; CD4+; helper T cell; helper T cells; regulatory T cell; regulatory T cells; Treg; Tregs; killer T cell; killer T cells; T-cell exhaustion; exhausted T cells

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/T_cell
- Wikipedia: https://en.wikipedia.org/wiki/T_cell

## Connected records

- terms: [Antigen](https://onco.cc/terms/antigen/), [B cell](https://onco.cc/terms/b-cell/), [Cytokine](https://onco.cc/terms/cytokine/), [Cytokine release syndrome (CRS)](https://onco.cc/terms/crs/), [Epitope](https://onco.cc/terms/epitope/), [Immune checkpoint](https://onco.cc/terms/immune-checkpoint/), [Immune system](https://onco.cc/terms/immune-system/), [Immunotherapy](https://onco.cc/terms/immunotherapy-term/), [Lymph node](https://onco.cc/terms/lymph-node/), [Lymphoma (tissue type)](https://onco.cc/terms/lymphoma-type/), [Neoantigen](https://onco.cc/terms/neoantigen/), [NK cell](https://onco.cc/terms/nk-cell/), [Tumour-infiltrating lymphocytes (TILs)](https://onco.cc/terms/tils/)
- technologies: [CAR-T cell therapy](https://onco.cc/technologies/car-t/), [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/), [T-cell engagers (bispecific)](https://onco.cc/technologies/t-cell-engager/), [TCR-T cell therapy](https://onco.cc/technologies/tcr-t/), [TIL therapy](https://onco.cc/technologies/til-therapy/)
- targets: [CD3](https://onco.cc/targets/cd3/), [CTLA-4](https://onco.cc/targets/ctla4/), [LAG-3](https://onco.cc/targets/lag3/), [PD-1](https://onco.cc/targets/pd1/), [PD-L1](https://onco.cc/targets/pdl1/)
- pathways: [PD-1 / PD-L1 immune checkpoint & T-cell activation](https://onco.cc/pathways/pd1-checkpoint/)
- people: [Robert Negrin](https://onco.cc/people/robert-negrin/)

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JSON: https://onco.cc/api/v1/entities/t-cell.json