T-helper cells are compartmentalized according to the cytokines they are able to produce. T-helper 1 cells produce interleukin-2 IL-2) and interferon-gamma (IFN-gamma), and develop following priming with IL-12. T-helper 2 cells produce IL-4, IL-5, and IL-10, and IL-4 is necessary to induce the differentiation of these cells. Type I IFNs have no direct effects on T-helper cell differentiation, but may regulate, especially in humans, the expression of the IL-12 receptor and thus influence T-helper 1 differentiation. On the other hand, type I IFNs can have inhibitory effects on the cytokine production by differentiated T-helper 1 cells. This suggests an important regulatory role for type I IFNs in adaptive immunity.

*Interferon Type I/PHYSIOLOGY *Th1 Cells/CYTOLOGY *Th2 Cells/CYTOLOGY

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