Section through HUVEC incubated with DAMP before fixation. The sections were double labeled with antibodies to dinitrophenol (DNP, small gold) and with anti-TFPI (large gold, arrowheads). The anti-DNP antibodies labeled the lumen of many intracellular organelles, indicating the presence of low pH. These organelles also labeled with anti-TFPI. Bar = 0.2 μm.