However, difficulties remain in correlating the forms of Nef with pathology, due to lack of standardization of the various assays for Nef, which are largely conducted in research laboratories46 Autoantibodies to FH, FB, FI, and C3b have also been found in atypical HUS, and presumably functionally mimic genetic deficiency of the control proteins.15 This evidence concerns the gene S100B and hemolytic-uremic syndrome.