CD4 and preeclampsia: Multiple highly cited articles appeared from 2001 to 2015.In the last 3 years, the heat of highly cited articles continues to the present, and the current research hotspots are immune imbalances, such as increased pro-inflammatory CD4+ T cells, decreased Treg, the Th1/Th2 immune balance, up-regulation Th17 cells, and regulatory cytokine IL-10, affecting the progression of preeclampsia.