Specificity of peptide-selected antisera to tandem repeat motifs. Synthetic peptides (50 amino acids, 2.5 repeats) from the tandem repeat portion of OGFr (A, C), the alternative reading frame of the OGFr tandem repeat region (B) or MUC1 (D) were plated at 1 µg/well. Peptide-selected antisera to the tandem repeat region of OGFr (filled circles), the alternative reading frame of OGFr (open circles) or a monoclonal antibody to MUC1 tandem repeats, VU4H5 (open triangles) were titrated against the peptide at the indicated concentrations. The antibodies were detected with anti-rabbit or mouse (for VU4H5) antibodies conjugated to HRP.