Effects of interleukin-17A on colonization and infection of respiratory tract bacteria

Interleukin-17A (IL-17A) is one of the proinflammatory cytokines produced by a subset of CD4+ T cells named Th17 cells. It plays a crucial role in both host innate and adaptive immune responses against colonization and infection of respiratory tract bacteria. Studies in animal models have demonstrated that IL-17A can induce the expressions of various chemokines, inflammatory factors and adhesion molecules via multiple intracellular signaling pathways and recruit neutrophils to infection sites. Moreover, recent studies have shown that single nucleotide polymorphisms (SNPs) of IL-17A coding gene can regulate the production of IL-17A in serum, resulting in individual difference in colonization rate by Streptococcus pneumoniae. This review presents recent data related to the structure, functions and signaling pathways of IL-17A, summarizes its roles in host defense based on studies in animal models and discusses the effects of genetic variation of IL-17A on colonization, susceptibility, clinical characteristics and disease prognosis of human respiratory tract bacteria. Key words: Interleukin-17A; Streptococcus pneumoniae; Single nucleotide polymorphism; Bacterial meningitis; Children