IL3 and Parkinson disease: Consistent with a previous study,[8] IL‐3 was colocalized with glial fibrillary acidic protein (GFAP), a marker of astrocytes, and IL‐3Rα was colocalized with ionized calcium binding adaptor molecule 1 (Iba1), a marker of microglia in the substantia nigra pars compacta (SNpc) of A53T PD mice (Figure 1D,E), suggesting that astrocytes are the source of IL‐3 and that microglia express IL‐3Rα.