IL-17 in Host Defense

Abstract

Many cell types including immune and nonimmune cells are able to produce IL-17 cytokines for host defense. In particular, innate immune cells such as γδT cells [1]. Recent studies indicate that γδT cells are the major initial IL-17 producers in acute infections [2]. Some γδT cells have IL-17-producing capacities without explicit induction of an immune response. These γδT cells preferentially reside in the skin and mucosal membranes [2]. Other innate immune cells producing IL-17 include NK, iNKT, mast cells, lymph tissue inducer (LTi) cells, group 3 innate lymphoid cells (ILC3) [3], and macrophages. Adoptive immune cells producing IL-17 include Th17 cells and Tc17 cells. Nonimmune cells include epithelial cells and keratinocytes, which are more likely for host defense. Adoptive immune cells producing IL-17 include Th17 cells and Tc17 cells. While CD8+ Tc17 cells are more likely to participate in host defense, CD4+ Th17 cells are more likely to participate in chronic inflammation in inflammatory diseases. ILC3 cells are found in the lung, gut, and skin. Currently, IL-17-producing ILC3 cells are often associated with inflammation [3–5], but their physiological property in host defense is not fully appreciated (Table 2.1) [6].