Decreased production of Th1 cytokines by stimulated peripheral leukocytes is found in malignant tumors. In patients with cancer of the kidney, prostate, and bladder the level of Th1 cytokines (IFN
and IL-2) was decreased and the level of Th2 cytokines (IL-4, IL-6, IL-10) was not affected. These data led to the conclusion that it is the function of the Th1 cytokines which is disturbed, but there is no shift from a Th1 to a Th2 profile (ElsasserBeile et al. 1998, 1999). The serum of cancer patients (breast cancer, colorectal cancer, ovarian cancer) contains substances which suppress the synthesis of IFN
by phytohemaglutinin (PHA)-stimulated peripheral blood mononuclear cells (Muster et al. 1996).