Interleukin-2, melatonin and interleukin-12 as a possible neuroimmune combination in the biotherapy of cancer.

Suppressive events induced by macrophages and TH2 lymphocytes would represent the most important factors responsible for the in vivo reduced efficacy of IL-2 cancer immunotherapy. Previous studies have shown that IL-3 or the pineal hormone MLT may abrogate macrophage-related suppressive events during IL-2 immunotherapy, while TH2-mediated immunosuppression is not neutralized by MLT or IL-3. On the basis of previous experimental data suggesting the inhibitory effect of IL-12 on TH2 activation, this preliminary study has been performed in an attempt to evaluate the influence of IL-12 on TH2 stimulation induced by IL-2 alone or IL-2 plus MLT, by evaluating the release of IL-10, which represents the main suppressive factor produced by TH2 lymphocytes. Pure lymphocyte cultures were incubated for 4 days with IL-2 (100 Cetus U/ml), MLT (100 pg/ml), IL-12 (1 ng/ml), IL-2 plus MLT, IL-2 plus IL-12 or IL-2 plus MLT and IL-12. Mean medium concentrations of IL-10 were measured by Elisa. IL-2 alone significantly stimulated IL-10 secretion with respect to the control medium alone, while no difference was observed with MLT alone or IL-12. IL-2-induced stimulation of IL-10 secretion was not abrogated by a concomitant MLT incubation. On the contrary, IL-12 significantly diminished IL-10 release in response to IL-2, and this inhibitory effect was more pronounced when IL-2 was added in association with both IL-12 and MLT. This preliminary study would suggest that the two most important immunosuppressive events occurring during IL-2 therapy, which are mediated by macrophages and TH2-lymphocytes, may be abrogated by a concomitant administration of MLT and IL-12, respectively. Therefore, the association of IL-12 could further amplify IL-2 efficacy with respect to IL-2 alone or IL-2 plus MLT.