KRT15 and hydrops fetalis: Nelson and colleagues found that activation of TLR3 by polyriboinosinic-polyribocytidylic acid (polyI: C), simulating the viral dsRNA in keratinocyte cell culture (Takada et al., 2017), causes a loss of Keratin1 and filaggrin (markers of differentiated keratinocytes) and an increase in the expression of Lgr5 and Lgr6 HF progenitor markers as well as Krt15 (Nelson et al., 2015).