Fluoxetine (10–6 M) suppresses IL-17, IFN-γ, and GM-CSF production by anti-CD3/CD28-activated CD4+ T-cells in RRMS patients and healthy subjects. 5-HT2B-receptor antagonist reduced the inhibitory effect of fluoxetine on cytokine production in MS patients. The gene discussed is IL17A; the disease is relapsing-remitting multiple sclerosis.