IL-6 is a sensitive marker of SI; among the 1211 patients with AD, the plasma level of IL-6 was normal upon admission in 3.3% (n = 40) of patients; 37 of them exhibited elevated plasma levels of other SI markers (TNF-α, IL-8, IL-10, IL-1RA, and CRP). The gene discussed is IL6; the disease is Alzheimer disease.