Peripheral blood samples from narcolepsy patients show increased levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, and major histocompatibility complex (MHC) class II, and reduced levels of chemokine receptor (CCR) 1 and CCR3, which are derived from microglia and macrophages, and IL-1 and TNF-α, which are well known to promote sleep in humans (Agnes et al., 2017). Here, IL6 is linked to narcolepsy.