Immunogenetics of human haptoglobins. II. Hp Bellevue, a cross-reacting mutant.

Using a radioimmunoassay method in conjunction with double diffusion studies, we characterized the antigenic determinants of the three Hp Bellevue phenotypes. An antigenic model based on these data indicates that each phenotype comprises a heterogeneous group of proteins with properties depending on their content of normal (hpbeta) and of mutant (hpbeta-Bellevue) chains of haptoglobin. The loss of the hemoglobin binding capacity and of a specific Hb-sensitive antigenic determinant is a consequence of the structural alteration in hpbeta-Bellevue and is expressed to various extents by the populations of proteins containing this chain. It is suggested that those molecules with a preponderance of mutant beta-chains are without significant hemoglobin binding capacity and are degraded more slowly in vivo than the ones capable of hemoglobin binding.