Cytokines in central nervous system trypanosomiasis: cause, effect or both?

The late, or encephalitic, stage of human African trypanosomiasis (HAT), or sleeping sickness, is typified by a diffuse meningoencephalitis characterised neuropathologically by perivascular infiltration of inflammatory cells. While the cause of this neuroinflammatory reaction is not understood, there is evidence for the roles of pro-inflammatory cytokines such as IFN-gamma and TNF-alpha and counter-inflammatory cytokines such as IL-10, with the balance of these influencing disease outcome. Because of the practical difficulties of obtaining serial measurements in patients, it has proved difficult to assign either cause or effect properties to measured cytokines, but mechanistic animal modelling studies are proving helpful.