The age-dependency of genetic and environmental influences on serum cytokine levels: A twin study

► Genetic and environmental factors in the regulation of 3 interleukins and TNF-α was investigated. ► We also modeled the possible role of age as a moderator on these influences. ► We demonstrate significant heritabilities on all investigated cytokines. ► We demonstrate moderation of environmental influences in regulation of IL1β and TNFα levels by age.