To identify the gene categories with differential expression in patients with or without PE, Gene Ontology analysis was carried out on the experiment data. The union of all differential expression genes resulted from data analysis are 2308 genes in patients with PE compared to patients without PE. Among them, 2238 genes are up-regulated and 70 are down-regulated. The main gene ontology categories impacted by these genes involve the up-regulation of 19 functioning categories against 4 down-regulation categories. Up-regulated genes are those genes whose functions are associated with transformation, phosphorylation, cell survival and cell conjugation, et al. While the function of down-regulated genes are relevant to the function of plasma membrane and activity of receptors, especially to the lymphocyte receptor complex and immunological synapse (Fig.4) . Gene ontology analysis exhibited compromised T cell mediated immune function, and t test indicated associated genes were significantly down-regulated in patients with PE than in control groups.