Reverse transcription-PCR (RT-PCR) amplification of reticulocyte RNAs from AC and AL Rh_nullpatients. The Rh and Rh50 cDNAs were amplified by RT-PCR from reticulocyte mRNAs as described in Materials and Methods. The Rh50 amplification products showed a smaller size in patient AC as compared with RhD-negative or RhD-positive controls, and no product is present in AL.