Native PR structure immune analyses

The partially purified B-receptors from T47D cells were used to immunize mice, and three monoclonal antibodies (MAbs) against human PR were produced. They 

Because it is B-specific and binds to native human PR, MAb PR-6 was used to study the nature of the association between the A- and B-proteins in the untransformed 8S state, and in the transformed 4S state [43]. This is of interest since there are conflicting models for the molecular interaction of the A- and B-proteins. One model holds that A and B dimerize [48,49] and that they are subunits of a larger holoreceptor the other model holds that A and B exist as separate 8S molecules [54,63]. 

PR-6 can also separate B-receptors from A-receptors that have been transformed to the 4S species by treatment with salt. Approximately half of the radioactivity seen in the 4S peak in the presence of control antibody is shifted to heavier aggregates upon addition of PR-6 and a secondary antibody. The control 4S peak contains both A and B, but only A remain at 4S after PR-6 addition while all the B-receptors shift to heavier sedimenting fractions. It appears then, that antibody PR-6 cross-reacts both with the native 8S as well as the transformed 4S form of B-receptors, and that 

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