[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Immunology](https://durgical.com/en/immunology/) › [Adaptive immunity](https://durgical.com/en/immunology/#a-adaptive) › Th1, Th2, Th17, Tfh and Treg

[Immunology](https://durgical.com/en/immunology/) · [Adaptive immunity](https://durgical.com/en/immunology/#a-adaptive)

# Th1, Th2, Th17, Tfh and Treg

- Topic

Helper T cells specialize into types that fight different germs, each with its own set of chemical signals.

Updated 2026-11-01

## Key points

- Th1: IL-12 in, IFN-γ out, macrophages, intracellular microbes, granulomas.
- Th2: IL-4 in, IL-4/IL-5/IL-13 out, IgE and eosinophils, helminths and allergy.
- Th17: TGF-β plus IL-6 in, IL-17/IL-22 out, neutrophils, Candida; psoriasis.
- Tfh: IL-21 and CD40L, germinal centers.
- Treg: FOXP3, IL-10 and TGF-β; FOXP3 loss causes IPEX.

## What it is

After activation, CD4 helper T cells differentiate according to the cytokines around them. Each subset has a master transcription factor and signature cytokines that suit a type of threat: Th1 for intracellular microbes, Th2 for helminths, Th17 for extracellular bacteria and fungi at mucosal surfaces, Tfh for helping B cells make antibodies, and Treg for keeping responses in check. When a subset is excessive or misdirected, it underlies typical diseases.

## Key facts

- IFN-γ inhibits Th2 cells and IL-4 inhibits Th1 cells, so the response tends to polarize.
- Treg cells are CD4+ CD25+ FOXP3+.
- Hyper-IgE syndrome with STAT3 mutation lacks Th17 cells: skin abscesses and candidiasis.
- In leprosy, a Th1 response gives the tuberculoid form and a Th2-skewed response the lepromatous form.

## CD4 helper subsets

| Subset | Induced by | Signature cytokines | Main function | Disease when excessive (or missing) |
| --- | --- | --- | --- | --- |
| [Th1 (T-bet)](https://durgical.com/en/conditions/tuberculosis/) | IL-12, IFN-γ | IFN-γ, IL-2 | Activates macrophages and CD8 T cells; intracellular microbes | Type IV hypersensitivity, granulomas; some organ-specific autoimmunity |
| [Th2 (GATA-3)](https://durgical.com/en/conditions/asthma/) | IL-4 | IL-4, IL-5, IL-13 | IgE class switch, eosinophils, mucus; helminths | Allergy, atopic asthma |
| Th17 (RORγt) | TGF-β plus IL-6 (IL-23 sustains) | IL-17, IL-22 | Recruits neutrophils; mucosal defense against bacteria and Candida | Psoriasis, inflammatory bowel disease; when missing, chronic mucocutaneous candidiasis |
| [Tfh (Bcl-6)](https://durgical.com/en/conditions/systemic-lupus-erythematosus/) | IL-6, IL-21 | IL-21 (plus CD40L, CXCR5) | Helps B cells in germinal centers: class switch and affinity maturation | High-affinity autoantibodies, as in lupus |
| Treg (FOXP3) | TGF-β, IL-2 | IL-10, TGF-β | Suppresses other T cells; peripheral tolerance | When missing, IPEX syndrome; excess can protect tumors |

## Clinical notes

- Defects in the IL-12/IFN-γ axis cause disseminated mycobacterial infections.
- Biologic drugs target subset cytokines: anti-IL-17 and anti-IL-23 in psoriasis, anti-IL-5 and anti-IL-4 receptor in severe eosinophilic or allergic disease.
- IPEX (FOXP3 mutation): early severe enteropathy, type 1 diabetes in infancy and eczema.

## Memory aid

Th1 calls the macrophage, Th2 calls the eosinophil, Th17 calls the neutrophil, Tfh trains the B cell and Treg calls for calm.

## Test yourself

Think of the answer, then tap the question to see it.

## Which cytokine from macrophages and dendritic cells drives Th1 differentiation?

IL-12.

## Which Th2 cytokine causes B cells to switch to IgE?

IL-4 (IL-13 also contributes).

## Which subset is deficient in hyper-IgE syndrome with STAT3 mutation, and what infections follow?

Th17 cells; patients have recurrent staphylococcal skin abscesses and chronic mucocutaneous candidiasis.

## Which transcription factor defines regulatory T cells?

FOXP3; its mutation causes IPEX syndrome.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/immunology/th1-th2-th17-tfh-and-treg/)

## Related

- [T-cell activation: two signals and superantigens](https://durgical.com/en/immunology/t-cell-activation-two-signals-and-superantigens/)
- [B-cell activation, class switching and affinity maturation](https://durgical.com/en/immunology/b-cell-activation-class-switching-and-affinity-maturation/)
- [Granulomatous inflammation](https://durgical.com/en/immunology/granulomatous-inflammation/)
- [Antibody structure and isotypes (IgG, IgA, IgM, IgE, IgD)](https://durgical.com/en/immunology/antibody-structure-and-isotypes/)
- [CD4⁺ helper T cell](https://durgical.com/en/immunology/cd4-helper-t-cell/)
- [Regulatory T cell (Treg, FOXP3)](https://durgical.com/en/immunology/regulatory-t-cell/)
- [Cytokines: the table to know](https://durgical.com/en/immunology/cytokines-the-table-to-know/)
- [Interferon-γ](https://durgical.com/en/immunology/interferon/)
- [IL-4, IL-5 and IL-13 (the Th2 cytokines)](https://durgical.com/en/immunology/il-4-il-5-and-il-13/)
- [Interleukin-17](https://durgical.com/en/immunology/interleukin-17/)
- [IL-12 and IL-23](https://durgical.com/en/immunology/il-12-and-il-23/)
- [IL-10 and TGF-β (the brakes)](https://durgical.com/en/immunology/il-10-and-tgf/)
- [Type I hypersensitivity (immediate, IgE)](https://durgical.com/en/immunology/type-i-hypersensitivity/)
- [Type IV hypersensitivity (delayed, T cells)](https://durgical.com/en/immunology/type-iv-hypersensitivity/)

## Related conditions

- [Asthma](https://durgical.com/en/conditions/asthma/)
- [Systemic lupus erythematosus](https://durgical.com/en/conditions/systemic-lupus-erythematosus/)
- [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/)

## Microorganisms

- [Mycobacterium tuberculosis](https://durgical.com/en/microbiology/mycobacterium-tuberculosis/)
- [Candida albicans](https://durgical.com/en/microbiology/candida-albicans/)

[← All of immunology](https://durgical.com/en/immunology/)

Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given.

Sources: [21.3 The Adaptive Immune Response: T lymphocytes and Their Functional Types](https://openstax.org/books/anatomy-and-physiology-2e/pages/21-3-the-adaptive-immune-response-t-lymphocytes-and-their-functional-types) (OpenStax (Anatomy and Physiology 2e), 2022); [18.3 T Lymphocytes and Cellular Immunity](https://openstax.org/books/microbiology/pages/18-3-t-lymphocytes-and-cellular-immunity) (OpenStax (Microbiology), 2016).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/immunology/th1-th2-th17-tfh-and-treg/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/immunology/th1-th2-th17-tfh-and-treg/