Figure 1.

Overview of the mammalian innate and adaptive immune systems and the regulatory effects of selected essential oils on various cytokines shown as dots (adapted from [11]). Antigen-presenting cells (APCs), such as dendritic cells or macrophages, are recruited to the infection site. The released cytokines further activate natural killer cells and lead to the maturation of T cells. The reviewed studies identified multiple cytokines that were downregulated by eucalyptus, tea tree, clove, and lavender EOs. Specific interleukins and other factors are also expressed in other cell types. Most reviewed research articles focused on monocytes and activated macrophages. Hence, only those effects are highlighted in the figure.