NK cells reconstituted 100 days after allogeneic transplantation are more frequently CD56^bright and display a distinctive repertoire of NK-cell receptors compared with the donor's NK cells. (A) Comparison of NKR expression in blood mononuclear cells of recipients 100 days after transplantation and their donors, as assessed by Q-RT-PCR of 15 individual NKR genes. For each gene the mean recipient/donor ratio obtained from analysis of 32 transplant pairs is shown. Not all KIR were analyzed for all transplant pairs, because one or more KIR genes were absent from the donor KIR genotype. Variation in the number of NK cells in the mononuclear cell fractions was corrected by normalization of the NKR transcript numbers to the NCAM (CD56) transcript number. Error bars indicate standard error of the mean (SEM). (B-E) Flow cytometric analysis comparing the surface expression of KIR (B-C) and NKG2A (D-E) on CD56⁺CD3⁻ gated NK cells from one representative transplant recipient (panels B,D) and the donor (panels C,E). The proportion of cells in each of the 4 quadrants is given as a percentage. The KIR analysis used a cocktail of the EB6, GL183, and DX9 mAbs.