# Antigen

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

## TL;DR

Anything an antibody or immune cell can recognise, typically a protein on a cell's surface. In cancer, an antigen is the flag that tells a drug or an immune cell 'this is the cell to attack'.

## Summary

Most cancer antigens are ordinary human proteins that a tumour makes in unusual amounts (HER2, TROP2, CD19, PSMA), so drugs targeting them also touch normal cells that carry a little; truly tumour-specific antigens arise from mutations (neoantigens) or from viral proteins. A good drug antigen is abundant on tumour cells, scarce on essential normal tissue, and stable over time. Tumours escape by losing the antigen, which is how CD19-negative relapse defeats CAR-T, and by hiding the pieces of antigen they would normally display to T cells.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: antigens; tumour antigen; tumour antigens; tumor antigen; tumor antigens; target antigen; target antigens; antigenic; tumour-associated antigen; tumour-associated antigens; tumor-associated antigen; tumor-associated antigens; antigen-negative; antigen loss

## Sources

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

## Connected records

- targets: [HER2](https://nuclide.cc/targets/her2/), [PSMA](https://nuclide.cc/targets/psma/), [TROP2](https://nuclide.cc/targets/trop2/)

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JSON: https://nuclide.cc/api/v1/entities/antigen.json