CXCL8 and atherosclerosis: Activation of the 5-HT4 and 7 receptor subtypes by means of serotonin triggered intracellular cyclic AMP (cAMP) signaling, which stimulated mRNA expression and subsequent cellular release of interleukin (IL)-1β, IL-6, IL-8/CXCL8, IL-12p40, and tumor necrosis factor (TNF)-α, which favor T-helper 2 cells that aid B-cell antibody secretion, as would be necessary for the development of atherosclerosis [121], while it had no effect on the production of IL-18 and interferon (IFN)-γ, which favor T-helper 1 cells involved in delayed-type hypersensitivity reactions [121].