Quantification of GRO-1 and MCP-1 secretion by ELISA. Concentration of GRO-1 oncogene (A) and MCP-1 chemotactic factor (B) are measured by ELISA in culture supernatants of controls and human endothelial cells treated with Stx1 or Stx2 holotoxin for 4 hours and 24 hours. Data are presented as mean from 3 independent experiments.