Human T-helper (Th) cell subtypes
| Type | Co-stimulatory cytokine | Transcription factors | Effector cytokines | Target |
| Th1 | IL-12 | T-bet, STAT1 | IFN-γ, TNF, IL-2 | Intracellular bacteria, viruses and mycobacteria |
| Th2 | IL-4 | STAT6, GATA3 | IL-4, IL-5, IL-13 | Extracellular parasites |
| Th17 | IL-23 | STAT3, RORγt | IL-17A, IL-17F, IL-21, IL-22 | Extracellular bacteria and fungi |
IL: interleukin; STAT: signal transducer and activator of transcription; IFN: interferon; TNF; tumour necrosis factor; RORγt: retinoic acid receptor-related orphan receptor γt.