Abstract
A method was developed using the AutoAnalyzer to study the binding characteristics of [human] anti-D with cells of various rhesus phenotypes. A positive association was demonstrated between site density and association constant. Two types of antigenic sites may be present on the cell surface recognized only by affinity differences. The higher affinity site binds both arms of an Ig[immunoglobulin]G anti-D molecule, whereas the lower affinity site binds only one.