IL6 and Alzheimer disease: Genetic variants in IL6 (7p15.3) and IL6R (1q21.3) genes have been supposed to affect the binding ability, expression levels and biological functions of the IL6-IL6R complex, contributing thereby to the onset and progression of severe infectious, autoimmune and neuroinflammatory/neurodegenerative diseases, including COVID-19, hepatitis B infection, rheumatoid arthritis (RA), cardiovascular disorders (CVD), multiple sclerosis (MS), Alzheimer’s disease (AD) and Parkinson’s disease (PD) [14,15,16,17].