Responses to Rh protein and peptides by PBMCs from healthy control donors. Representative experiments showing absent or weak proliferation by PBMCs from healthy D-positive (A-B) and D-negative (C) control donors after stimulation with panels of overlapping 15-mer peptides spanning the sequences of the RhD (A-B) or Rhce (C) proteins (▪) or purified RhD protein (▨). Control unstimulated cultures were also included (□). Peptides are numbered 1 to 68 from the N-terminus: the ce panel lacks numbers 7, 9, 13, 15, 17, 19, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 43, 45, 49, 51, 53, 55, 57, 59, 64, and 66. The dotted line indicates the level of response taken as representing a positive response (SI > 3). Error bars indicate SD.