For PD, N-α-syn, the dominant protein in dopaminergic neuronal inclusions, induces potent neurotoxic Teffs that can accelerate nigrostriatal degeneration.5, 32 Transformation of Teff responses by Tregs leads to significant dopaminergic neuronal protection3 and proportional changes in numbers of interferon-γ-producing Th1, IL-4-producing Th2, and CD4+CD25+ T cells are linked to the tempo of disease progression.14, 33 However, whether sargramostim-induced changes in T cell profiles could affect PD pathobiology remained unknown. This evidence concerns the gene IL4 and Parkinson disease.