Sellin et al. observed an increase of Foxp3+ Tregs as a consequence of MV infection of CD150-transgenic mice in spleen and brain [32], which suggests that also the MV-infection itself supports the expansion and migration of Tregs, and that these infection-induced Tregs may be part of the multifactorial MV-induced immunosuppression [3], [4]. The gene discussed is FOXP3; the disease is infection.