Trypanosoma brucei (Tb). In experimental Tb infections, a molecule re/eased from the trypanosomes has been isolated that binds to the CD8 molecule of T cells, whereby T cells are activated to secrete interferon?. This cytokine brads to the parasites and triggers them to proliferate, establishing a peculiar b/directional activating signal system. The hypothesis is presented that the molecules involved in these bidirectional signals might also interact with neurons, thus causing brain dysfunctions. Studies on the molecular interactions between parasites and the nervous system in sleeping sickness might reveal basic mechanisms underlying other neuropsychiatric diseases.

Parasitic infections of the nervous system include diseases, such as African sleeping sickness, Chagas' disease and cerebral malaria, that represent major health problems. However, their important neurological complications are relatively neglected and have received little attention in basic neuroscience research. Of particular interest is African sleeping sickness, caused by the extracellular haemoflagellate Trypanosoma brucei (Tb) that includes three sub-