Recombinant cytokines as an approach to immune reconstitution in aging

Aging is characterized by a decreased humoral and cell-mediated immunity to a large variety of exogenous antigens and by an increased propensity to autoantibody production, suggesting an age-related disregulation of the immune system. The decline in immune responsiveness to exogenous antigens has been attributed to thymus involution, consisting of a fall in the capacity to induce intrathymic T-cell growth and differentiation, and also to export mature T cells to the periphery. T-cell activation and secretion of soluble factors have been reported to change with aging, but, as with cytokines, the results are conflicting. We investigated the production of IL-2 and IFN-gamma (Th1 type) and IL-4 (Th2 type) cytokines by mitogen-activated spleen cells from young, adult and old mice and their regulation by the addition of a recombinant cytokine (IL-1 beta, IL-2, IL-3, IL-4, IL-12, IFN-gamma) at varying concentrations. The results indicate that cytokine production can be enhanced only when it is deficient, suggesting the possible use of recombinant cytokines as efficient immunomodulators in age-associated immune disorders.