Figure 1: Differentiation of naïve T helper cells into particular subsets. T helper lymphocytes leaving the thymus (naïve or TH0) are not yet fully differentiated to perform their specific functions in peripheral lymphoid tissues. They are endowed of these properties in the process of their interactions with dendritic cells (DCs) that engulf, process, and present antigens to them. Moreover, DCs in dependence of the processed antigens produce different cytokines. If DCs produce IL-12, naïve T cells polarise into the TH1 subset, if IL-4 into the TH2 subset and eventually, if DCs synthesise IL-6, naïve T helper cells will become the TH17 cells.