A study of different rhesus phenotypes and their binding characteristics

A method has been developed using the Auto Analyzer to study the binding characteristics of anti-D with cells of various rhesus phenotypes. A positive association has been demonstrated between site density and association constant. A hypothesis is proposed for the presence of two types of antigenic sites on the cell surface recognised only by affinity difference. The high affinity site binds both arms of an IgG anti-D molecule, whereas the low affinity site binds only one.