Proliferative responses to the panel of K and k Kell peptides by PBMCs from unimmunized control donorsare not focused on particular sequences. (A) Summary map of responses by PBMCs from 10 unimmunized control donors to the panel of peptides spanning the M₁₉₃ (K) and T₁₉₃ (k) polymorphism. Filled boxes represent positive proliferative responses (SI > 3). There is no significant difference between the numbers of responses to K or k peptides and no peptide elicited responses in > 60% of donors. (B) Representative proliferative responses to the Kell peptide panel by PBMCs from unimmunized control donors 2, 6, and 8. Dotted line denotes the level of proliferation taken as representing a positive response (SI > 3). These examples illustrate that responses to peptide 1M(_179-193) do not predominate, while other peptides can elicit proliferation, including k sequences. PBMCs from all donors proliferated significantly in response to the control recall Ag PPD.