Capewell et al. (71) reported that IL-21 is a cause of the severity of human African trypanosomiasis, while Stumhofer et al. (68) found that IL-21 plays a key role in shaping the humoral and cellular response to Toxoplasma gondii, but they also indicated that IL-21 has a limited role in regulating immunopathology. The gene discussed is IL21; the disease is human African trypanosomiasis.