The cytokine production potential of immunocompetent cells from the blood of stomach adenocarcinoma patients was analyzed after the pretreatment of cells with the HLDF differentiation factor with subsequent exposure to polyclonal activators (HLDF+PA). IL-1β, IL-1Ra, TNFα, IL-2, IL-6, IL-8, IL-10, IL-17, IL-18, IL-18BPa, IFNγ, G-CSF, and GM-CSF were quantified in the supernatants after precipitation of the cells. Specific effects of HLDF+PA were manifested as an increase in the production of IL-8, IL-17, and GM-CSF due to suppression of Th1-dependent immune reactions in a Th17-mediated mechanism that is a part of a broader functional antagonism of Th1 and Th17 lymphocyte subpopulations.