Understanding how ICOS regulates the development and the survival of EM CD4 cells may enhance novel vaccination strategies aimed at inducing protective EM CD4 T cells [41], [44] and regulatory strategies to control CD4 responses in diseases such as atopic asthma that are exacerbated by EM CD4 T cells [47], [48], [49], [50], [51], [52]. The gene discussed is ICOS; the disease is atopic asthma.