Immunogenetics of human haptoglobins. I. The antigenic structure of normal Hp phenotypes.

The various antigenic determinants of serum haptoglobins (Hp) may be studied semiquantitatively in a radioimmunoassay system. Using three antisera of overlapping specificities, we constructed an antigenic model of the various Hp phenotypes comprising four distinct determinants. This adds a new determinant, situated near the hemoglobin binding site, to the three determinants reported in the literature. The assay system is sensitive to 0.2 mug or less of serum Hp. Furthermore, it can detect determinants that are not recognized by double diffusion studies.