Hypoxanthine Derivatives in Experimental Infections

In vivo treatment with parenterally administered hypoxanthinederivatives, notably ST 789, was able to protect cyclophosphamide-immunosuppressed mice againstexperimental infections with both bacterial and fungal pathogens. However, the mechanisms accountingfor these effects of hypoxanthine derivatives remain to be fully established. In fact, only the treatment withST 789 resulted in a clear enhancement of the primary antibody production as well as macrophagephagocytic activity, whereas T lymphocyte responsiveness to mitogens and both macrophage- and naturalkiller-dependent cytotoxicity were not significantly affected. These data, together with the recently shownability of ST 789 to increase interleukin-6 production, suggest that monocyte/macrophages are likely to be the main cellular target of the immunomodulating activity of ST 789. Finally, in the presentln vivo study, hypoxanthine derivatives did not enhance the mean survival time of tumour-bearing immunosuppressed mice