Fig 1: Independent binding assay confirms that circulating levels of CD33 protein in G156TfsTer5 homozygous carriers are below detection level.(A) G156TfsTerHis, which is missing most of the Ig-C2 domain that is recognized by 3D6 antibody, is poorly detected in the ELISA format shown in Fig 4B. (B) An ELISA assay designed with rabbit anti-human CD33 polyclonal antibody rT16-PA (Cat# 12238-T16, SinoBiological; immunogen = M1-H259 of CD33) to capture CD33 polypeptides followed by detection with hSGL3 antibody can directly detect G156TfsTer5. Signals from purified, recombinant CD33MECDHis and G156TfsTer5His tag constructs are shown. (C) Reformatting of hSGL3 to a murine constant region (mSGL3) preserves detection of G156TfsTer5 protein. (D). Measurement of G156TFsTer5 levels in select participant sera samples from the recall by genotype study. Homozygous reference: “0” genotype; Heterozygous carrier:“1” genotype; Homozygous G156TfsTer5 carrier: “2” genotype.