PBMCs from control RhD-negative donors, who have not been alloimmunized, rarely proliferate when stimulated with peptides from the RhD protein sequence.

Shown here are the proliferative responses of PBMCs from 3 control unimmunized RhD-negative donors (A, B, and C) against the panel of peptides spanning the RhD protein. The broken line indicates the level of proliferation assumed to represent a positive response (the higher of SI = 3 or cpm = 1000).