DLL1 and hand, foot and mouth disease: We also found significant increases in the expression levels of Notch ligands Dll1 and Dll4 in the peripheral blood of children with HFMD, suggesting that Notch signaling might be initiated and activated during HFMD via the engagement of upregulated Notch ligand Dll1 or Dll4 with Notch receptors, which subsequently affects the differentiation and development of T and B lymphocytes.