In vitro combined effects of human interferons and interleukin-2 on natural cell-mediated cytotoxicity

Interferon-Beta combined with interleukin-2 restores human natural cytotoxicity impaired in vitro by ionizing radiations

It is well known that ionizing radiations induce a marked downregulation of antigen-dependent and natural immunity for a prolonged period of time. This is due, at least in part, to radiation-induced apoptosis of different lymphocyte subpopulations, including natural killer (NK) cells. Aim of this study was to investigate the capability of Beta Interferon (β-IFN) and Interleukin-2 (IL2), alone or in combination, to restore the functional activity of the natural immune system. Mononuclear cells (MNCs) obtained from intact or in vitro irradiated human peripheral blood were treated in vitro with β-IFN immediately before or at the end of the 4-day treatment with IL2. Time-course analysis was performed on the NK activity, the total number and the apoptotic fraction of CD16+ and CD56+ cells, the 2 main NK effector cell subpopulations. The results indicate that radiation-induced impairment of natural cytotoxicity of MNC could be successfully antagonized by the β-IFN+IL2 combination, mainly when exposure to β-IFN preceded IL2 treatment. This radioprotective effect is paralleled by lower levels of radiation-induced apoptosis and increased expression of the antiapoptotic Bcl-2 protein. Since natural immunity can play a significant role in antitumor host's resistance, these results could provide the rational basis for a cytokine-based pharmacological strategy able to restore immune responsiveness and to afford possible therapeutic benefits in cancer patients undergoing radiotherapy.

In vivo augmentation of IFN-gamma with a rIL-12 human/mouse chimera: pleiotropic effects against infectious agents in mice and rats

A heterodimer containing the mouse 35 kDa and human 40 kDa subunit of IL-12 was expressed in COS cells (cIL-12). Administration of 25-200 U of the cIL-12-COS supernatant to mice twice daily for 2 days augmented spleen cell IFN-gamma production in response to IL-2 and peritoneal macrophage activity (superoxide and nitrites) as compared to animals receiving mock transfected supernatants. cIL-12 also increased levels of IFN-gamma in serum but most dramatically following an LPS injection (50-fold over controls). Animals pretreated with cIL-12 suffered enhanced mortality following challenge with the Gram negative organism E. coli but enhanced survival or clearance following infection with the Gram positive organisms L. monocytogenes and S. aureus. Although daily treatment of mice with cIL-12 following an intranasal influenza A infection elevated levels of IFN-gamma in the bronchioalveolar lavage fluid three-fold over controls, neither prophylactic or therapeutic treatment with the same dose level decreased viral titres in the lung. In addition, no effect was observed in animals infected with encephalomyocarditis virus or respiratory syncytial virus. Therefore, cIL-12 is a potent in vivo augmentor of IFN-gamma production. It has differential effects on infectious disease depending on the invading organism and time of administration; being efficacious for intracellular bacteria but ineffective at the same dose levels against viral diseases.