During an inflammatory response, P-selectin is expressed on endothelial cells first, followed by E-selectin later. Stimuli such as histamine and thrombin cause endothelial cells to mobilize immediate release of preformed P-selectin from Weible-Palade bodies inside the cell. Cytokines such as TNF-alpha stimulate transcription and translation of E-selectin and additional P-selection, which account for the delay of several hours.[7]