We used two controls in the protection experiments. In one control we challenged the cells with bacterial supernatant without adding liposomes, to determine that the baseline cytotoxicity is in line with the results displayed in the Figure 1. The second control consists of the immune cells without toxin or liposomes. This control represents 100% survival and allows us to normalize our survival data. We also tested the intrinsic toxicity of liposomes on their own to see if they did impede cell growth or were cytotoxic. At the concentrations used in current study the liposomes were not cytotoxic (data not shown). The following text was added to the material and method section: The data were normalized to a control incubated with PBS instead of bacterial supernatant (considered as 0% cell death). A control challenged by bacterial supernatant without liposomes was added for each assay to verify the expected cytotoxic activity 2.
In the current work we do not intend to reveal new neutralization mechanisms either for SLO or for SLS.