Introduction 1 2 Escherichia coli 1 3 4 5 6 7 8 9 10 11 12 k 13 14 15 16 17 18 19 19 17 20 We postulated that, as the monocyte has a specific receptor, it might also function as a carrier to transport Stx to the renal endothelium. To investigate this hypothesis, Stx was loaded to isolated monocytes from healthy donors and coincubated with target cells [vero cells and human umbilical cord venous endothelial cells (HUVEC)]. The level of transfer was determined by measuring the protein synthesis of these target cells and the transfer of fluorescein isothiocyanate (FITC)-labeled B subunit of Stx1 with flow cytometry. Materials and methods Materials 125 19 21 22 23 3 Culture of vero cells and HUVEC 24 Isolation of monocytes and loading with Stx2 17 Coincubation Stx2-loaded monocytes and target cells n n 6 3 6 5 n 19 25 Study of supernatant Stx-loaded monocytes n 3 125 n 6 125 Statistics P Results Coincubation Stx2-loaded monocytes and target cells 1 2 Fig. 1 n n 3 P  Fig. 2 white bar black bar  n Study of supernatant Stx-loaded monocytes 3 125 1 Fig. 3 n P  Table 1 125 Stx-loaded cells Before 4→37°C (cpm) After 4→37°C (cpm) Vero cells 1,034,383 671,060 Monocytes donor 1 1,437 427 Monocytes donor 2 1,070 374 Monocytes donor 3 1,121 677 cpm Transfer of Stx to target cells without change in temperature n 4 Fig. 4 white black grey x-axis y-axis a b c  Discussion 17 26 18 5 Fig. 5 a b c  27 28 29 As renal endothelial damage is already present after the occurrence of clinical symptoms of HUS, it is very important to develop efficacious early prevention. Understanding the mechanism in which the toxin is specifically targeted to the kidney can lead to novel intervention strategies.