Differential sensitivity of human leukocyte-derived cell lines to Shiga toxin

Shiga toxin (Stx)-producing Escherichia coli (STEC) cause diarrhea and hemorrhagic colitis in humans, sometimes followed by potentially fatal complications like neurologic damage and the hemolytic-uremic syndrome (HUS). Stx is produced in the intestine, but causes vascular damage in specific target tissues such as brain and kidney, resulting in systemic complications. The way Stx enters the circulation and is transported from the gut to the target organs is not clarified yet. Stx binding and transport through the circulation by blood cells is currently discussed. Therefore, we investigated the expression of the Stx glycosphingolipid (GSL) receptors globotriaosylceramide (Gb3Cer) and globotetraosylceramide (Gb4Cer) on four leukocyte-derived cell lines, representing monocytes, granulocytes, T and B lymphocytes. Stx-receptors were analyzed by thin-layer chromatography and immunodetection. Subsequently sensitivity towards Stx was investigated using a commercially available cytotoxicity assay. The monocytic cell line expressed both Gb3Cer and Gb4Cer, and presence of Gb3Cer but lack of Gb4Cer were characteristic features of the B cell descendant. Importantly, T cell and granulocyte descendants lacked any globo-series GSLs. Results of the cytotoxicity assay were consistent with these findings: viability of both the monocytic cell line and the B cell descendant were decreased after treatment with Stx, whereas the granulocyte and T cell lines remained resistant upon Stx exposure. Due to the lack of Stx-receptors Gb3Cer and Gb4Cer in the granulocyte- and T cell derived cell lines, it seems rather unlikely that granulocytes or T cells could act as "transporters" of Stx to target endothelial cells of the human vasculature.