Proliferative responses to the panel of K and k Kell peptides by PBMCs from K-alloimmunized women are focused on K sequences. (A) Summary map of responses by PBMCs from 10 K-alloimmunized women to the panel of peptides spanning the M₁₉₃ (K) and T₁₉₃ (k) polymorphism. Filled boxes represent positive proliferative responses (SI > 3). K peptides elicited more responses than k (χ² test P < .001), and K peptide 1M(_179-193) was the predominant stimulatory sequence (90% donors were positive). (B) Representative proliferative responses to the Kell peptide panel by PBMCs from alloimmunized donors 1, 2, and 5. Dotted line denotes the level of proliferation taken as representing a positive response (SI > 3). These examples illustrate that, despite the predominance of responses to peptide 1M(_179-193), other peptides can elicit proliferation, including k sequences. PBMCs from all donors proliferated significantly in response to the control recall Ag PPD.