The effect of season on cytokine expression in multiple sclerosis and healthy subjects

We measured the levels of IFNγ, TNFα, Il-4 and Il-10 produced by mitogen-stimulated peripheral blood mononuclear cells (PBMC) from healthy people, and those with the relapse/remitting form of multiple sclerosis. Blood was taken in summer and winter. Healthy people had a summer excess of Il-4, Il-10 and TNFα, and a winter excess of IFNγ. Untreated MS cases had a summer excess of Il-10, whereas those treated with Interferon-beta had lower levels of all cytokines, and displayed no seasonal effect.