During evolution, immunity has been developed to protect against invading
organisms and remove unwanted structures, like malignant cells. Yet, in extreme cases
the organisms, like bacteria or parasites, find their way through tissues and can survive
even in blood, which contains most elements of the immune system. A drastic example
is parasitic Schistosoma mansoni worms that can live within blood vessels for years.
Imaging studies have helped us to visualize ways how Schistosoma parasites can
escape immune attacks inside circulation. Parasites often escape the immune system by
hijacking soluble inhibitors of the blood complement inhibitors. By molecular
radioimaging it is also possible to trace the accumulation of these inhibitors to their
targets. Specifically, our collaborative work has been able to demonstrate the
acquisition of immunoglobulins by adult S. mansoni worms and show the distribution
of the complement inhibitor factor H in live animals. Radioimaging can thus be applied
not only to detection of tumors and their metastases but to analysis of immune
reactions against endogenous and exogenous targets in vivo.