Donors who express HLA-B*1302 or HLA-B*1301 make very few KIR3DL1-dependent NK cells. NK cells from 9 donors (donors 1-9) were tested in the CD107a assay to determine their ability to make KIR3DL1-dependent NK clones. Each donor was incubated with the class I bare target 721.221, targets lacking either the C1 or C2 epitopes (data not shown), or targets lacking only the Bw4 epitope (HLA-A*0301, 1101, B*0702, 3501, C*0401, 0702). (A) Representative examples of flow cytometry showing identification of KIR3DL1⁺, CD158a,b⁻ NK cells and their subsequent CD107a expression when incubated with 721.221 or the Bw4⁻ target. Numbers on plots are percentages of total displayed cells. (B) After incubation with the Bw4⁻ target, the proportion of KIR3DL1⁺, CD158a,b⁻ NK cells that were CD107a⁺ did not distinguish donors with HLA-B*13 from donors with other Bw4⁺ alleles and donors homozygous for Bw6. (C) The proportion of KIR3DL1⁺, CD158a,b⁻ NK cells does not distinguish HLA-B*13 donors from donors with other Bw4⁺ alleles and donors homozygous for Bw6. (D) The proportion of KIR3DL1-dependent NK clones of the total NK-cell population distinguishes HLA-B*13 donors from donors with other Bw4⁺ alleles. A total of 2% to 3% of NK cells from donors with other Bw4⁺ alleles are KIR3DL1 dependent, whereas this is true of less than 1% of NK cells from HLA-B*13 donors. Less than 0.5% of NK clones from donors homozygous for Bw6 are KIR3DL1 dependent, slightly less than donors with HLA-B13. Error bars represent SEM.