An increasing frequency of anti-Stx antibodies has been reported in higher-age population which is in general refractory to HUS. In addition, anti-Stx2 seroreactivity has been correlated with the absence of symptoms in family outbreaks of STEC infection. This evidence together with the almost null recurrence of the enteropathic form of this disease, suggest that HUS resistance may be associated with increasing immunity, possibly to Stx2. In spite of the high circulation of STEC strains in Argentina,Doxorubicin in particular those producing Stx2, local information about the frequencies of anti-Stx2/Stx1 antibodies in HUS cases and healthy children is very limited. This is because, at least in part, the evaluation of anti-Stx2/Stx1 antibodies is not routinely done by clinical laboratories. Although the presence of neutralizing activity in HUS patient’s sera by using Vero cell monolayers is routinely performed by the National Reference Laboratory from the National Health Surveillance System, it is known that a very low neutralizing activity is generally observed and not in all patients. For this reason, several authors have reported more sensitive tests such as ELISA or immunoblotting assay for anti-Shiga toxin antibodies detection. Our work indicates that Western blotting and ELISA can be successfully used also in Argentina to detect antibodies to Stx2 in both healthy and HUS children. Since both methods combine different antigenic proteins: B subunit of Stx2 or the whole holotoxin,Epoxomicin either native or denatured, they probably detect different antibodies thus enhancing the spectrum of antibody detection. It is interesting to highlight that the association between the positive results obtained by ELISA and WB techniques was stronger in HUS group than in NHC or HUSrec groups, probably as a consequence of higher antibody titers in plasma from HUS group than those in plasma from NHC or HUSrec groups. Moreover, the simultaneous evaluation by the two methods allowed us to differentiate HUS acute patients from normal healthy children with a great specificity and accuracy, in order to confirm the HUS etiology when nonpathogenic bacteria were isolated from stools.