In vivo, expression levels of interferon (IFN)-alpha, IFN-beta, IFN-gamma, IL-1beta, IL-2, IL-3, IL-15, IL-17F, IL-18 and colony-stimulating factor (CSF)-1 are significantly down-regulated, whereas interleukin (IL)-4, IL-10, IL-13 and tumour necrosis factor (TNF)-alpha are markedly increased in PBMCs at all stages of infection. The gene discussed is IL17F; the disease is infection.