Identification of candidate HEV genes under control of the tissue microenvironment by DNA microarray analysis. In the first screen, to select for genes with preferential expression in HEV compared with flat vessel endothelium, DNA microarrays (Atlas Human 1.2 and Cardiovascular Arrays) were hybridized with probes corresponding to HEVECs freshly isolated from human tonsils (D0 HEVECs) or to HUVECs freshly isolated from human umbilical vein (D0 HUVECs). In the second screen, HEV genes rapidly down-regulated ex vivo were identified by hybridizing the microarrays with probes prepared from freshly isolated HEVECs without any cell culture step (D0 HEVECs) or HEVECs cultured for 2 days (D2 HEVECs). Arrows indicate spots corresponding to DARC, which is preferentially expressed in HEVECs (first screen) and rapidly down-regulated outside the lymphoid tissue microenvironment (second screen).