DLL4 and hand, foot and mouth disease: The Dll4 expression levels showed negative correlations with CD3+ and CD3+CD8+ cell subsets, but a positive correlation with CD3−CD19+ cell subset that has the B lymphocyte surface antigen characteristics, suggesting that the up-regulated Dll4 expression may be associated with a relatively inhibited status of CD3+ lymphocytes and a relatively activated status of CD3−CD19+ lymphocytes observed in children with HFMD.