Bacterial and protozoan infections have the ability to suppress neoplastic growth, a process assumed to be due to concomitant cell-mediated anti-tumour immunity. In the May Journal of Immunology Christopher Hunter and colleagues from the University of Pennsylvania, Philadelphia show that suppression of tumour neovascularization is a novel mechanism essential for infection-induced resistance to tumours.

Hunter et al injected melanoma cells into normal and immunocompromised mice and found that in both situations an acute infection with Toxoplasma gondii effectively blocked neoplastic growth. In immunocompromised mice the effect was independent of cytotoxic T or NK cells, production of NO by macrophages or the function of the cytokines IL-12 and TNF-α but was accompanied by strong suppression of angiogenesis inside the nascent tumor. This suppression resulted in severe hypoxia and avascular necrosis that arrested neoplastic growth (J Immunol 2001, 166: 5878-5881).

T. gondii is unlikely to be used in the...

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