# CD4

Source: https://onco.cc/targets/cd4/  
OnCo record `cd4` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

CD4 is the marker of helper T cells, the cells that direct an immune response rather than kill infected or cancerous cells themselves. A CD4 count is how the strength of that arm of the immune system is measured.

## Summary

CD4 is a surface co-receptor that binds MHC class II and defines the helper T cell lineage. Helper T cells do not kill target cells directly; they license other cells to, which is why a CD4 count is the standard measure of that arm of the immune system in transplant, infection and after chemotherapy. CD4 is also present at lower levels on monocytes, macrophages and dendritic cells. In an immunophenotyping panel CD4 and CD8 are the pair that split the T cell compartment, and nearly every statement on this site about T cell infiltration or recovery rests on them. CD4 is separately known as the receptor HIV uses to enter cells.

## Fields

- Kind: Target
- Last checked: 2026-10-16
- Also known as: CD4 molecule; T4
- Tags: immune-marker
- Symbol: CD4
- Class: surface-antigen
- Biology: Co-receptor on helper T cells; binds MHC class II and marks the helper lineage.
- Where found: Helper T cells; Monocytes and macrophages; Dendritic cells

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/CD4
- HGNC:1678: https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:1678

## Connected records

- targets: [CD8](https://onco.cc/targets/cd8/), [CXCR5](https://onco.cc/targets/cxcr5/), [HLA-DR](https://onco.cc/targets/hla-dr/)
- terms: [T cell](https://onco.cc/terms/t-cell/)

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JSON: https://onco.cc/api/v1/entities/cd4.json