Problem: Cytokine production of monocytes and lymphocytes differs between males and females. This difference is characterized by a decreased percentage of interleukin (IL)-2-producing lymphocytes and an increased percentage of IL-12, IL-1β and tumour necrosis factor (TNF)-α-producing monocytes in males compared with females. In the present study, we investigated whether testosterone may explain these differences.
Method of study: Stimulated whole blood of healthy woman was incubated with different concentrations of testosterone. Intracellular lymphocyte production of IL-2 and interferon (IFN)-γ, as well as intracellular monocyte production of IL-12, IL-1β and TNF-α were measured using flow cytometry.
Results: A significant increased percentage of IL-12- and IL-1β-producing monocytes was found after incubation with physiological concentrations of testosterone. No effect of testosterone was found on IL-2- and IFN-γ-producing lymphocytes and TNF-α-producing monocytes.
Conclusions: The increased percentage of IL-12- and IL-1β-producing monocytes in males compared with females in vivo may be induced by testosterone, as the in vitro percentage of IL-12- and IL-1β-producing monocytes is increased after incubation with physiological concentrations of testosterone.