As Shh treatment increased human Treg differentiation in vitro, and in mice, decreasing Hh levels in Shh+/– skin increased AD severity, but increasing Shh expression in Gli3+/– skin decreased AD severity, we hypothesized that individuals who suffer from AD might have lower baseline levels of expression of Hh pathway components in skin than healthy individuals. The gene discussed is SHH; the disease is Alzheimer disease.