Elevation of IL-12 p40 and its antibody in myasthenia gravis with thymoma.

We examined the serum levels of cytokines, interferon (IFN)-alpha, IFN-gamma, interleukin (IL)-4, IL-12 p40, and IL-12 p70; those that affect the T helper 1 and 2 balance in patients with myasthenia gravis (MG). Among the cytokines tested, only IL-12 p40, together with the serum titer of anti-IL-12 p40 antibody, was significantly elevated in MG with thymoma. Their elevation was independent of the histopathology of thymoma. Thymectomy decreased the levels of IL-12 p40 accompanied by the anti-acetylcholine receptor antibody, but not anti-IL-12 p40 antibodies. These data strongly suggest the association of IL-12 p40 and its autoantibody with the immunopathology of MG with thymoma.